DBI - Database independent interface for Perl
SYNOPSIS
use DBI;
@driver_names = DBI->available_drivers;
@data_sources = DBI->data_sources($driver_name, \%attr);
$dbh = DBI->connect($data_source, $username, $auth, \%attr);
$rv = $dbh->do($statement);
$rv = $dbh->do($statement, \%attr);
$rv = $dbh->do($statement, \%attr, @bind_values);
$ary_ref = $dbh->selectall_arrayref($statement);
$ary_ref = $dbh->selectall_hashref($statement);
$ary_ref = $dbh->selectcol_arrayref($statement);
$ary_ref = $dbh->selectrow_arrayref($statement);
@row_ary = $dbh->selectrow_array($statement);
$sth = $dbh->prepare($statement);
$sth = $dbh->prepare_cached($statement);
$rv = $sth->bind_param($p_num, $bind_value);
$rv = $sth->bind_param($p_num, $bind_value, $bind_type);
$rv = $sth->bind_param($p_num, $bind_value, \%attr);
$rv = $sth->execute;
$rv = $sth->execute(@bind_values);
$rc = $sth->bind_col($col_num, \$col_variable);
$rc = $sth->bind_columns(@list_of_refs_to_vars_to_bind);
@row_ary = $sth->fetchrow_array;
$ary_ref = $sth->fetchrow_arrayref;
$hash_ref = $sth->fetchrow_hashref;
$ary_ref = $sth->fetchall_arrayref;
$rv = $sth->rows;
$rc = $dbh->commit;
$rc = $dbh->rollback;
$sql = $dbh->quote($string);
$rc = $h->err;
$str = $h->errstr;
$rv = $h->state;
$rc = $dbh->disconnect;
GETTING HELP
If you have questions about DBI, you can get help from the
dbi-users@perl.org mailing list. You can subscribe to the
list by emailing:
dbi-users-help@perl.org
Also worth a visit is the DBI home page at:
http://dbi.perl.org/
Before asking any questions, reread this document, consult
the archives and read the DBI FAQ. The archives are listed
at the end of this document. The FAQ is installed as a
DBI::FAQ module so you can read it by executing `perldoc
DBI::FAQ'.
Please note that Tim Bunce does not maintain the mailing
lists or the web page (generous volunteers do that). So
please don't send mail directly to him; he just doesn't
have the time to answer questions personally. The dbi-
users mailing list has lots of experienced people who
should be able to help you if you need it.
NOTE
This is the DBI specification that corresponds to the DBI
version 1.17 (`$Date: 2001/06/04 17:20:21 $').
The DBI specification is evolving at a steady pace, so
it's important to check that you have the latest copy. The
RECENT CHANGES section below has a summary of user-visible
changes. The Changes file supplied with the DBI holds more
detailed change information.
Note also that whenever the DBI changes, the drivers take
some time to catch up. Recent versions of the DBI have
added new features (marked NEW in the text) that may not
yet be supported by the drivers you use. Talk to the
authors of those drivers if you need the features.
Extensions to the DBI and other DBI related modules use
the `DBIx::*' namespace. See the Naming Conventions and
Name Space entry elsewhere in this document and:
http://www.perl.com/CPAN/modules/by-module/DBIx/
Here is a brief summary of significant user-visible
changes in recent versions. (If a recent version isn't
mentioned, it simply means that there were no significant
user-visible changes in that version.)
DBI 1.15
Added selectall_hashref, selectrow_hashref, selec
trow_arrayref methods.
DESCRIPTION
The DBI is a database access module for the Perl program
ming language. It defines a set of methods, variables,
and conventions that provide a consistent database inter
face, independent of the actual database being used.
It is important to remember that the DBI is just an inter
face. The DBI is a layer of "glue" between an application
and one or more database driver modules. It is the driver
modules which do most of the real work. The DBI provides a
standard interface and framework for the drivers to oper
ate within.
Architecture of a DBI Application
|<- Scope of DBI ->|
.-. .--------------. .-------------.
.-------. | |---| XYZ Driver |---| XYZ Engine |
| Perl | | | `--------------' `-------------'
| script| |A| |D| .--------------. .-------------.
| using |--|P|--|B|---|Oracle Driver |---|Oracle Engine|
| DBI | |I| |I| `--------------' `-------------'
| API | | |...
|methods| | |... Other drivers
`-------' | |...
`-'
The API, or Application Programming Interface, defines the
call interface and variables for Perl scripts to use. The
API is implemented by the Perl DBI extension.
The DBI "dispatches" the method calls to the appropriate
driver for actual execution. The DBI is also responsible
for the dynamic loading of drivers, error checking and
handling, providing default implementations for methods,
and many other non-database specific duties.
Each driver contains implementations of the DBI methods
using the private interface functions of the corresponding
database engine. Only authors of sophisticated/multi-
database applications or generic library functions need be
concerned with drivers.
The following conventions are used in this document:
$dbh Database handle object
$sth Statement handle object
$drh Driver handle object (rarely seen or used in applications)
$h Any of the handle types above ($dbh, $sth, or $drh)
$rc General Return Code (boolean: true=ok, false=error)
$rv General Return Value (typically an integer)
@ary List of values returned from the database, typically a row of data
$rows Number of rows processed (if available, else -1)
$fh A filehandle
undef NULL values are represented by undefined values in Perl
\%attr Reference to a hash of attribute values passed to methods
Note that Perl will automatically destroy database and
statement handle objects if all references to them are
deleted.
Outline Usage
To use DBI, first you need to load the DBI module:
use DBI;
use strict;
(The `use strict;' isn't required but is strongly recom
mended.)
Then you need to the connect entry elsewhere in this docu
ment to your data source and get a handle for that connec
tion:
$dbh = DBI->connect($dsn, $user, $password,
{ RaiseError => 1, AutoCommit => 0 });
Since connecting can be expensive, you generally just con
nect at the start of your program and disconnect at the
end.
Explicitly defining the required `AutoCommit' behavior is
strongly recommended and may become mandatory in a later
version. This determines whether changes are automati
cally committed to the database when executed, or need to
be explicitly committed later.
The DBI allows an application to "prepare" statements for
later execution. A prepared statement is identified by a
statement handle held in a Perl variable. We'll call the
Perl variable `$sth' in our examples.
The typical method call sequence for a `SELECT' statement
is:
execute, fetch, fetch, ...
execute, fetch, fetch, ...
execute, fetch, fetch, ...
for example:
$sth = $dbh->prepare("SELECT foo, bar FROM table WHERE baz=?");
$sth->execute( $baz );
while ( @row = $sth->fetchrow_array ) {
print "@row\n";
}
The typical method call sequence for a non-`SELECT' state
ment is:
prepare,
execute,
execute,
execute.
for example:
$sth = $dbh->prepare("INSERT INTO table(foo,bar,baz) VALUES (?,?,?)");
while(<CSV>) {
chomp;
my ($foo,$bar,$baz) = split /,/;
$sth->execute( $foo, $bar, $baz );
}
The `do()' method can be used for non repeated
non-`SELECT' statement (or with drivers that don't support
placeholders):
$rows_affected = $dbh->do("UPDATE your_table SET foo = foo + 1");
To commit your changes to the database (when the AutoCom
mit entry elsewhere in this document is off):
$dbh->commit; # or call $dbh->rollback; to undo changes
Finally, when you have finished working with the data
source, you should the disconnect entry elsewhere in this
document from it:
$dbh->disconnect;
The DBI does not have a concept of a "current session".
Every session has a handle object (i.e., a `$dbh')
returned from the `connect' method. That handle object is
used to invoke database related methods.
Most data is returned to the Perl script as strings. (Null
values are returned as `undef'.) This allows arbitrary
precision numeric data to be handled without loss of accu
racy. Beware that Perl may not preserve the same accuracy
when the string is used as a number.
Dates and times are returned as character strings in the
current default format of the corresponding database
engine. Time zone effects are database/driver dependent.
Perl supports binary data in Perl strings, and the DBI
will pass binary data to and from the driver without
change. It is up to the driver implementors to decide how
they wish to handle such binary data.
Most databases that understand multiple character sets
have a default global charset. Text stored in the database
is, or should be, stored in that charset; if not, then
that's the fault of either the database or the application
that inserted the data. When text is fetched it should be
automatically converted to the charset of the client, pre
sumably based on the locale. If a driver needs to set a
flag to get that behavior, then it should do so; it should
not require the application to do that.
Multiple SQL statements may not be combined in a single
statement handle (`$sth'), although some databases and
drivers do support this (notably Sybase and SQL Server).
Non-sequential record reads are not supported in this ver
sion of the DBI. In other words, records can only be
fetched in the order that the database returned them, and
once fetched they are forgotten.
Positioned updates and deletes are not directly supported
by the DBI. See the description of the `CursorName'
attribute for an alternative.
Individual driver implementors are free to provide any
private functions and/or handle attributes that they feel
are useful. Private driver functions can be invoked using
the DBI `func()' method. Private driver attributes are
accessed just like standard attributes.
Many methods have an optional `\%attr' parameter which can
be used to pass information to the driver implementing the
method. Except where specifically documented, the `\%attr'
In general, you can ignore `\%attr' parameters or pass it
as `undef'.
Naming Conventions and Name Space
The DBI package and all packages below it (`DBI::*') are
reserved for use by the DBI. Extensions and related mod
ules use the `DBIx::' namespace (see
`http://www.perl.com/CPAN/modules/by-module/DBIx/').
Package names beginning with `DBD::' are reserved for use
by DBI database drivers. All environment variables used
by the DBI or by individual DBDs begin with "`DBI_'" or
"`DBD_'".
The letter case used for attribute names is significant
and plays an important part in the portability of DBI
scripts. The case of the attribute name is used to sig
nify who defined the meaning of that name and its values.
Case of name Has a meaning defined by
------------ ------------------------
UPPER_CASE Standards, e.g., X/Open, ISO SQL92 etc (portable)
MixedCase DBI API (portable), underscores are not used.
lower_case Driver or database engine specific (non-portable)
It is of the utmost importance that Driver developers only
use lowercase attribute names when defining private
attributes. Private attribute names must be prefixed with
the driver name or suitable abbreviation (e.g., "`ora_'"
for Oracle, "`ing_'" for Ingres, etc).
Driver Specific Prefix Registry:
ado_ DBD::ADO
best_ DBD::BestWins
csv_ DBD::CSV
db2_ DBD::DB2
f_ DBD::File
file_ DBD::TextFile
ib_ DBD::InterBase
ing_ DBD::Ingres
ix_ DBD::Informix
msql_ DBD::mSQL
mysql_ DBD::mysql
odbc_ DBD::ODBC
ora_ DBD::Oracle
pg_ DBD::Pg
proxy_ DBD::Proxy
rdb_ DBD::RDB
sapdb_ DBD::SAP_DB
solid_ DBD::Solid
syb_ DBD::Sybase
tdat_ DBD::Teradata
tuber_ DBD::Tuber
uni_ DBD::Unify
xbase_ DBD::XBase
SQL - A Query Language
Most DBI drivers require applications to use a dialect of
SQL (Structured Query Language) to interact with the
database engine. The following links provide useful
information and further links about SQL:
http://www.altavista.com/query?q=sql+tutorial
http://www.jcc.com/sql_stnd.html
http://www.contrib.andrew.cmu.edu/~shadow/sql.html
The DBI itself does not mandate or require any particular
language to be used; it is language independent. In ODBC
terms, the DBI is in "pass-thru" mode, although individual
drivers might not be. The only requirement is that queries
and other statements must be expressed as a single string
of characters passed as the first argument to the the pre
pare entry elsewhere in this document or the do entry
elsewhere in this document methods.
For an interesting diversion on the real history of RDBMS
and SQL, from the people who made it happen, see:
http://ftp.digital.com/pub/DEC/SRC/technical-notes/SRC-1997-018-html/sqlr95.html
Follow the "And the rest" and "Intergalactic dataspeak"
links for the SQL history.
Some drivers support placeholders and bind values. Place
holders, also called parameter markers, are used to indi
cate values in a database statement that will be supplied
later, before the prepared statement is executed. For
example, an application might use the following to insert
a row of data into the SALES table:
INSERT INTO sales (product_code, qty, price) VALUES (?, ?, ?)
or the following, to select the description for a product:
SELECT description FROM products WHERE product_code = ?
The `?' characters are the placeholders. The association
of actual values with placeholders is known as binding,
and the values are referred to as bind values.
When using placeholders with the SQL `LIKE' qualifier, you
must remember that the placeholder substitutes for the
whole string. So you should use "`... LIKE ? ...'" and
include any wildcard characters in the value that you bind
to the placeholder.
Null Values
Undefined values, or `undef', can be used to indicate null
values. However, care must be taken in the particular
case of trying to use null values to qualify a `SELECT'
statement. Consider:
SELECT description FROM products WHERE product_code = ?
Binding an `undef' (NULL) to the placeholder will not
select rows which have a NULL `product_code'! Refer to the
SQL manual for your database engine or any SQL book for
the reasons for this. To explicitly select NULLs you have
to say "`WHERE product_code IS NULL'" and to make that
general you have to say:
... WHERE (product_code = ? OR (? IS NULL AND product_code IS NULL))
and bind the same value to both placeholders.
Performance
Without using placeholders, the insert statement shown
previously would have to contain the literal values to be
inserted and would have to be re-prepared and re-executed
for each row. With placeholders, the insert statement only
needs to be prepared once. The bind values for each row
can be given to the `execute' method each time it's
called. By avoiding the need to re-prepare the statement
faster. Here's an example:
my $sth = $dbh->prepare(q{
INSERT INTO sales (product_code, qty, price) VALUES (?, ?, ?)
}) or die $dbh->errstr;
while (<>) {
chomp;
my ($product_code, $qty, $price) = split /,/;
$sth->execute($product_code, $qty, $price) or die $dbh->errstr;
}
$dbh->commit or die $dbh->errstr;
See the executeand bind_param entries elsewhere in this
document for more details.
The `q{...}' style quoting used in this example avoids
clashing with quotes that may be used in the SQL state
ment. Use the double-quote like `qq{...}' operator if you
want to interpolate variables into the string. See the
Quote and Quote-like Operators entry in the perlop manpage
for more details.
See also the the bind_column entry elsewhere in this docu
ment method, which is used to associate Perl variables
with the output columns of a `SELECT' statement.
THE DBI PACKAGE AND CLASS
In this section, we cover the DBI class methods, utility
functions, and the dynamic attributes associated with
generic DBI handles.
DBI Constants
The following SQL standard type constants can be imported
individually or, by importing the special `:sql_types'
tag, all together:
SQL_CHAR SQL_NUMERIC SQL_DECIMAL SQL_INTEGER SQL_SMALLINT
SQL_FLOAT SQL_REAL SQL_DOUBLE SQL_VARCHAR
SQL_DATE SQL_TIME SQL_TIMESTAMP
SQL_LONGVARCHAR SQL_BINARY SQL_VARBINARY SQL_LONGVARBINARY
SQL_BIGINT SQL_TINYINT
SQL_WCHAR SQL_WVARCHAR SQL_WLONGVARCHAR
SQL_BIT
SQL_ALL_TYPES
See the the type_info, type_info_all, and bind_param
entries elsewhere in this document methods for possible
uses.
The following methods are provided by the DBI class:
`connect'
$dbh = DBI->connect($data_source, $username, $password)
or die $DBI::errstr;
$dbh = DBI->connect($data_source, $username, $password, \%attr)
or die $DBI::errstr;
Establishes a database connection, or session, to the
requested `$data_source'. Returns a database handle
object if the connection succeeds. Use `$dbh-'>`dis
connect' to terminate the connection.
If the connect fails (see below), it returns `undef'
and sets both `$DBI::err' and `$DBI::errstr'. (It does
not set `$!', etc.) You should generally test the
return status of `connect' and `print $DBI::errstr' if
it has failed.
Multiple simultaneous connections to multiple
databases through multiple drivers can be made via the
DBI. Simply make one `connect' call for each database
and keep a copy of each returned database handle.
The `$data_source' value should begin with
"`dbi:'driver_name`:'". The driver_name specifies the
driver that will be used to make the connection. (Let
ter case is significant.)
As a convenience, if the `$data_source' parameter is
undefined or empty, the DBI will substitute the value
of the environment variable `DBI_DSN'. If just the
driver_name part is empty (i.e., the `$data_source'
prefix is "`dbi::'"), the environment variable
`DBI_DRIVER' is used. If neither variable is set, then
`connect' dies.
Examples of `$data_source' values are:
dbi:DriverName:database_name
dbi:DriverName:database_name@hostname:port
dbi:DriverName:database=database_name;host=hostname;port=port
There is no standard for the text following the driver
name. Each driver is free to use whatever syntax it
wants. The only requirement the DBI makes is that all
the information is supplied in a single string. You
must consult the documentation for the drivers you are
using for a description of the syntax they require.
(Where a driver author needs to define a syntax for
the `$data_source', it is recommended that they follow
the ODBC style, shown in the last example above.)
(and the driver in `$data_source' is not "`Proxy'")
then the connect request will automatically be changed
to:
dbi:Proxy:$ENV{DBI_AUTOPROXY};dsn=$data_source
and passed to the DBD::Proxy module. `DBI_AUTOPROXY'
is typically set as "`hostname=...;port=...'". See the
DBD::Proxy documentation for more details.
If `$username' or `$password' are undefined (rather
than just empty), then the DBI will substitute the
values of the `DBI_USER' and `DBI_PASS' environment
variables, respectively. The DBI will warn if the
environment variables are not defined. However, the
everyday use of these environment variables is not
recommended for security reasons. The mechanism is
primarily intended to simplify testing.
`DBI-'>`connect' automatically installs the driver if
it has not been installed yet. Driver installation
either returns a valid driver handle, or it dies with
an error message that includes the string
"`install_driver'" and the underlying problem. So
`DBI-'>`connect' will die on a driver installation
failure and will only return `undef' on a connect
failure, in which case `$DBI::errstr' will hold the
error message.
The `$data_source' argument (with the "`dbi:...:'"
prefix removed) and the `$username' and `$password'
arguments are then passed to the driver for process
ing. The DBI does not define any interpretation for
the contents of these fields. The driver is free to
interpret the `$data_source', `$username', and `$pass
word' fields in any way, and supply whatever defaults
are appropriate for the engine being accessed. (Ora
cle, for example, uses the ORACLE_SID and TWO_TASK
environment variables if no `$data_source' is speci
fied.)
The `AutoCommit' and `PrintError' attributes for each
connection default to "on". (See the AutoCommitand
PrintError entries elsewhere in this document for more
information.) However, it is strongly recommended
that you explicitly define `AutoCommit' rather than
rely on the default. Future versions of the DBI may
issue a warning if `AutoCommit' is not explicitly
defined.
The `\%attr' parameter can be used to alter the
default settings of `PrintError', `RaiseError', `Auto
Commit', and other attributes. For example:
PrintError => 0,
AutoCommit => 0
});
You can also define connection attribute values within
the `$data_source' parameter. For example:
dbi:DriverName(PrintError=>0,Taint=>1):...
Individual attributes values specified in this way
take precedence over any conflicting values specified
via the `\%attr' parameter to `connect'.
The `dbi_connect_method' attribute can be used to
specify which driver method should be called to estab
lish the connection. The only useful values are 'con
nect', 'connect_cached', or some specialized case like
'Apache::DBI::connect' (which is automatically the
default when running within Apache).
Where possible, each session (`$dbh') is independent
from the transactions in other sessions. This is use
ful when you need to hold cursors open across transac
tions--for example, if you use one session for your
long lifespan cursors (typically read-only) and
another for your short update transactions.
For compatibility with old DBI scripts, the driver can
be specified by passing its name as the fourth argu
ment to `connect' (instead of `\%attr'):
$dbh = DBI->connect($data_source, $user, $pass, $driver);
In this "old-style" form of `connect', the
`$data_source' should not start with
"`dbi:driver_name:'". (If it does, the embedded
driver_name will be ignored). Also note that in this
older form of `connect', the `$dbh-'>`{AutoCommit}'
attribute is undefined, the `$dbh-'>`{PrintError}'
attribute is off, and the old `DBI_DBNAME' environment
variable is checked if `DBI_DSN' is not defined.
Beware that this "old-style" `connect' will be with
drawn in a future version of DBI.
`connect_cached' NEW
$dbh = DBI->connect_cached($data_source, $username, $password)
or die $DBI::errstr;
$dbh = DBI->connect_cached($data_source, $username, $password, \%attr)
or die $DBI::errstr;
`connect_cached' is like the connect entry elsewhere
in this document, except that the database handle
returned is also stored in a hash associated with the
nect_cached' with the same parameter values, then the
corresponding cached `$dbh' will be returned if it is
still valid. The cached database handle is replaced
with a new connection if it has been disconnected or
if the `ping' method fails.
Note that the behavior of this method differs in sev
eral respects from the behavior of presistent connec
tions implemented by Apache::DBI.
Caching can be useful in some applications, but it can
also cause problems and should be used with care. The
exact behavior of this method is liable to change, so
if you intend to use it in any production applications
you should discuss your needs on the dbi-users mailing
list.
The cache can be accessed (and cleared) via the the
CachedKids entry elsewhere in this document attribute.
`available_drivers'
@ary = DBI->available_drivers;
@ary = DBI->available_drivers($quiet);
Returns a list of all available drivers by searching
for `DBD::*' modules through the directories in
`@INC'. By default, a warning is given if some drivers
are hidden by others of the same name in earlier
directories. Passing a true value for `$quiet' will
inhibit the warning.
`data_sources'
@ary = DBI->data_sources($driver);
@ary = DBI->data_sources($driver, \%attr);
Returns a list of all data sources (databases) avail
able via the named driver. If `$driver' is empty or
`undef', then the value of the `DBI_DRIVER' environ
ment variable is used.
The driver will be loaded if it hasn't been already.
Note that if the driver loading fails then it dies
with an error message that includes the string
"`install_driver'" and the underlying problem.
Data sources are returned in a form suitable for pass
ing to the the connect entry elsewhere in this docu
ment method (that is, they will include the
"`dbi:$driver:'" prefix).
Note that many drivers have no way of knowing what
data sources might be available for it. These drivers
return an empty or incomplete list or may require
database handle, to be supplied.
`trace'
DBI->trace($trace_level)
DBI->trace($trace_level, $trace_filename)
DBI trace information can be enabled for all handles
using the `trace' DBI class method. To enable trace
information for a specific handle, use the similar
`$h-'>`trace' method described elsewhere.
Trace levels are as follows:
0 - Trace disabled.
1 - Trace DBI method calls returning with results or errors.
2 - Trace method entry with parameters and returning with results.
3 - As above, adding some high-level information from the driver
and some internal information from the DBI.
4 - As above, adding more detailed information from the driver.
Also includes DBI mutex information when using threaded Perl.
5 and above - As above but with more and more obscure information.
Trace level 1 is best for a simple overview of what's
happening. Trace level 2 is a good choice for general
purpose tracing. Levels 3 and above (up to 9) are
best reserved for investigating a specific problem,
when you need to see "inside" the driver and DBI.
The trace output is detailed and typically very use
ful. Much of the trace output is formatted using the
the neat entry elsewhere in this document function, so
strings in the trace output may be edited and trun
cated.
Initially trace output is written to `STDERR'. If
`$trace_filename' is specified and can be opened in
append mode then all trace output (including that from
other handles) is redirected to that file. A warning
is generated is the file can't be opened. Further
calls to `trace' without a `$trace_filename' do not
alter where the trace output is sent. If `$trace_file
name' is undefined, then trace output is sent to
`STDERR' and the previous trace file is closed. The
`trace' method returns the previous tracelevel.
See also the `$h-'>`trace' and `$h-'>`trace_msg' meth
ods and the the DEBUGGING entry elsewhere in this doc
ument section for information about the `DBI_TRACE'
environment variable.
In addition to the methods listed in the previous section,
the DBI package also provides these utility functions:
`neat'
$str = DBI::neat($value, $maxlen);
Return a string containing a neat (and tidy) represen
tation of the supplied value.
Strings will be quoted, although internal quotes will
not be escaped. Values known to be numeric will be
unquoted. Undefined (NULL) values will be shown as
`undef' (without quotes). Unprintable characters will
be replaced by dot (.).
For result strings longer than `$maxlen' the result
string will be truncated to `$maxlen-4' and "`...''"
will be appended. If `$maxlen' is 0 or `undef', it
defaults to `$DBI::neat_maxlen' which, in turn,
defaults to 400.
This function is designed to format values for human
consumption. It is used internally by the DBI for the
trace entry elsewhere in this document output. It
should typically not be used for formatting values for
database use. (See also the quote entry elsewhere in
this document.)
`neat_list'
$str = DBI::neat_list(\@listref, $maxlen, $field_sep);
Calls `DBI::neat' on each element of the list and
returns a string containing the results joined with
`$field_sep'. `$field_sep' defaults to `", "'.
`looks_like_number'
@bool = DBI::looks_like_number(@array);
Returns true for each element that looks like a num
ber. Returns false for each element that does not
look like a number. Returns `undef' for each element
that is undefined or empty.
DBI Dynamic Attributes
Dynamic attributes are always associated with the last
handle used (that handle is represented by `$h' in the
descriptions below).
Where an attribute is equivalent to a method call, then
refer to the method call for all related documentation.
but they do have limitations. Specifically, they have a
short lifespan: because they are associated with the last
handle used, they should only be used immediately after
calling the method that "sets" them. If in any doubt, use
the corresponding method call.
`$DBI::err'
Equivalent to `$h-'>`err'.
`$DBI::errstr'
Equivalent to `$h-'>`errstr'.
`$DBI::state'
Equivalent to `$h-'>`state'.
`$DBI::rows'
Equivalent to `$h-'>`rows'. Please refer to the docu
mentation for the the rows entry elsewhere in this
document method.
`$DBI::lasth'
Returns the DBI object handle used for the most recent
DBI method call. If the last DBI method call was a
DESTROY then $DBI::lasth will return the handle of the
parent of the destroyed handle, if there is one.
METHODS COMMON TO ALL HANDLES
The following methods can be used by all types of DBI han
dles.
`err'
$rv = $h->err;
Returns the native database engine error code from the
last driver method called. The code is typically an
integer but you should not assume that.
The DBI resets $h->err to undef before most DBI method
calls, so the value only has a short lifespan. Also,
most drivers share the same error variables across all
their handles, so calling a method on one handle will
typically reset the error on all the other handles
that are children of that driver.
If you need to test for individual errors and have
your program be portable to different database
engines, then you'll need to determine what the corre
sponding error codes are for all those engines and
test for all of them.
`errstr'
$str = $h->errstr;
the last driver method called. This has the same
lifespan issues as the the err entry elsewhere in this
document method described above.
`state'
$str = $h->state;
Returns an error code in the standard SQLSTATE five
character format. Note that the specific success code
`00000' is translated to '' (false). If the driver
does not support SQLSTATE (and most don't), then state
will return `S1000' (General Error) for all errors.
The driver is free to return any value via `state',
e.g., warning codes, even if it has not declared an
error by returning a true value via the the err entry
elsewhere in this document method described above.
`trace'
$h->trace($trace_level);
$h->trace($trace_level, $trace_filename);
DBI trace information can be enabled for a specific
handle (and any future children of that handle) by
setting the trace level using the `trace' method.
Trace level 1 is best for a simple overview of what's
happening. Trace level 2 is a good choice for general
purpose tracing. Levels 3 and above (up to 9) are
best reserved for investigating a specific problem,
when you need to see "inside" the driver and DBI. Set
`$trace_level' to 0 to disable the trace.
The trace output is detailed and typically very use
ful. Much of the trace output is formatted using the
the neat entry elsewhere in this document function, so
strings in the trace output may be edited and trun
cated.
Initially, trace output is written to `STDERR'. If
`$trace_filename' is specified, then the file is
opened in append mode and all trace output (including
that from other handles) is redirected to that file.
Further calls to trace without a `$trace_filename' do
not alter where the trace output is sent. If
`$trace_filename' is undefined, then trace output is
sent to `STDERR' and the previous trace file is
closed.
See also the `DBI-'>`trace' method and the DEBUGGING
entry elsewhere in this document for information about
the `DBI_TRACE' environment variable.
$h->trace_msg($message_text);
$h->trace_msg($message_text, $min_level);
Writes `$message_text' to the trace file if trace is
enabled for `$h' or for the DBI as a whole. Can also
be called as `DBI-'>`trace_msg($msg)'. See the trace
entry elsewhere in this document.
If `$min_level' is defined, then the message is output
only if the trace level is equal to or greater than
that level. `$min_level' defaults to 1.
`func'
$h->func(@func_arguments, $func_name);
The `func' method can be used to call private non-
standard and non-portable methods implemented by the
driver. Note that the function name is given as the
last argument.
This method is not directly related to calling stored
procedures. Calling stored procedures is currently
not defined by the DBI. Some drivers, such as
DBD::Oracle, support it in non-portable ways. See
driver documentation for more details.
ATTRIBUTES COMMON TO ALL HANDLES
These attributes are common to all types of DBI handles.
Some attributes are inherited by child handles. That is,
the value of an inherited attribute in a newly created
statement handle is the same as the value in the parent
database handle. Changes to attributes in the new state
ment handle do not affect the parent database handle and
changes to the database handle do not affect existing
statement handles, only future ones.
Attempting to set or get the value of an unknown attribute
is fatal, except for private driver specific attributes
(which all have names starting with a lowercase letter).
Example:
$h->{AttributeName} = ...; # set/write
... = $h->{AttributeName}; # get/read
`Warn' (boolean, inherited)
Enables useful warnings for certain bad practices.
Enabled by default. Some emulation layers, especially
those for Perl 4 interfaces, disable warnings. Since
warnings are generated using the Perl `warn' function,
they can be intercepted using the Perl
`Active' (boolean, read-only)
True if the handle object is "active". This is rarely
used in applications. The exact meaning of active is
somewhat vague at the moment. For a database handle it
typically means that the handle is connected to a
database (`$dbh-'>`disconnect' sets `Active' off).
For a statement handle it typically means that the
handle is a `SELECT' that may have more data to fetch.
(Fetching all the data or calling `$sth-'>`finish'
sets `Active' off.)
`Kids' (integer, read-only)
For a driver handle, `Kids' is the number of currently
existing database handles that were created from that
driver handle. For a database handle, `Kids' is the
number of currently existing statement handles that
were created from that database handle.
`ActiveKids' (integer, read-only)
Like `Kids', but only counting those that are `Active'
(as above).
`CachedKids' (hash ref)
For a database handle, returns a reference to the
cache (hash) of statement handles created by the the
prepare_cached entry elsewhere in this document
method. For a driver handle, returns a reference to
the cache (hash) of database handles created by the
the connect_cached entry elsewhere in this document
method.
`CompatMode' (boolean, inherited)
Used by emulation layers (such as Oraperl) to enable
compatible behavior in the underlying driver (e.g.,
DBD::Oracle) for this handle. Not normally set by
application code.
`InactiveDestroy' (boolean)
This attribute can be used to disable the database
engine related effect of DESTROYing a handle (which
would normally close a prepared statement or discon
nect from the database etc).
For a database handle, this attribute does not disable
an explicit call to the disconnect method, only the
implicit call from DESTROY.
This attribute is specifically designed for use in
Unix applications that "fork" child processes. Either
the parent or the child process, but not both, should
set `InactiveDestroy' on all their shared handles.
Note that some databases, including Oracle, don't
`PrintError' (boolean, inherited)
This attribute can be used to force errors to generate
warnings (using `warn') in addition to returning error
codes in the normal way. When set "on", any method
which results in an error occuring will cause the DBI
to effectively do a `warn("$class $method failed:
$DBI::errstr")' where `$class' is the driver class and
`$method' is the name of the method which failed.
E.g.,
DBD::Oracle::db prepare failed: ... error text here ...
By default, `DBI-'>`connect' sets `PrintError' "on".
If desired, the warnings can be caught and processed
using a `$SIG{__WARN__}' handler or modules like
CGI::Carp and CGI::ErrorWrap.
`RaiseError' (boolean, inherited)
This attribute can be used to force errors to raise
exceptions rather than simply return error codes in
the normal way. It is "off" by default. When set
"on", any method which results in an error will cause
the DBI to effectively do a `die("$class $method
failed: $DBI::errstr")', where `$class' is the driver
class and `$method' is the name of the method that
failed. E.g.,
DBD::Oracle::db prepare failed: ... error text here ...
If you turn `RaiseError' on then you'd normally turn
`PrintError' off. If `PrintError' is also on, then
the `PrintError' is done first (naturally).
Typically `RaiseError' is used in conjunction with
`eval { ... }' to catch the exception that's been
thrown and followed by an `if ($@) { ... }' block to
handle the caught exception. In that eval block the
$DBI::lasth variable can be useful for diagnosis and
reporting. For example, $DBI::lasth->{Type} and
$DBI::lasth->{Statement}.
If you want to temporarily turn `RaiseError' off
(inside a library function that is likely to fail, for
example), the recommended way is like this:
{
local $h->{RaiseError}; # localize and turn off for this block
...
}
The original value will automatically and reliably be
exited. The same logic applies to other attributes,
including `PrintError'.
Sadly, this doesn't work for Perl versions up to and
including 5.004_04. Even more sadly, for Perl 5.5 and
5.6.0 it does work but leaks memory! For backwards
compatibility, you could just use `eval { ... }'
instead.
`ShowErrorStatement' (boolean, inherited) NEW
This attribute can be used to cause the relevant
Statement text to be appended to the error messages
generated by the `RaiseError' and `PrintError'
attributes. Only applies to errors on statement han
dles plus the prepare() and do() database handle meth
ods. (The exact format of the appended text is sub
ject to change.)
`ChopBlanks' (boolean, inherited)
This attribute can be used to control the trimming of
trailing space characters from fixed width character
(CHAR) fields. No other field types are affected, even
where field values have trailing spaces.
The default is false (although it is possible that the
default may change). Applications that need specific
behavior should set the attribute as needed. Emulation
interfaces should set the attribute to match the
behavior of the interface they are emulating.
Drivers are not required to support this attribute,
but any driver which does not support it must arrange
to return `undef' as the attribute value.
`LongReadLen' (unsigned integer, inherited)
This attribute may be used to control the maximum
length of long fields ("blob", "memo", etc.) which the
driver will read from the database automatically when
it fetches each row of data. The `LongReadLen'
attribute only relates to fetching and reading long
values; it is not involved in inserting or updating
them.
A value of 0 means not to automatically fetch any long
data. (`fetch' should return `undef' for long fields
when `LongReadLen' is 0.)
The default is typically 0 (zero) bytes but may vary
between drivers. Applications fetching long fields
should set this value to slightly larger than the
longest long field value to be fetched.
Some databases return some long types encoded as pairs
to the underlying data length and not the doubled-up
length of the encoded string.
Changing the value of `LongReadLen' for a statement
handle after it has been `prepare''d will typically
have no effect, so it's common to set `LongReadLen' on
the `$dbh' before calling `prepare'.
Note that the value used here has a direct effect on
the memory used by the application, so don't be too
generous.
See the LongTruncOk entry elsewhere in this document
for more information on truncation behavior.
`LongTruncOk' (boolean, inherited)
This attribute may be used to control the effect of
fetching a long field value which has been truncated
(typically because it's longer than the value of the
`LongReadLen' attribute).
By default, `LongTruncOk' is false and so fetching a
long value that needs to be truncated will cause the
fetch to fail. (Applications should always be sure to
check for errors after a fetch loop in case an error,
such as a divide by zero or long field truncation,
caused the fetch to terminate prematurely.)
If a fetch fails due to a long field truncation when
`LongTruncOk' is false, many drivers will allow you to
continue fetching further rows.
See also the LongReadLen entry elsewhere in this docu
ment.
`Taint' (boolean, inherited)
If this attribute is set to a true value and Perl is
running in taint mode (e.g., started with the `-T'
option), then all data fetched from the database is
tainted, and the arguments to most DBI method calls
are checked for being tainted. This may change.
The attribute defaults to off, even if Perl is in
taint mode. See the perlsec manpage for more about
taint mode. If Perl is not running in taint mode,
this attribute has no effect.
When fetching data that you trust you can turn off the
Taint attribute, for that statement handle, for the
duration of the fetch loop.
Currently only fetched data is tainted. It is possible
that the results of other DBI method calls, and the
future versions. That change may well break your
applications unless you take great care now. If you
use DBI Taint mode, please report your experience and
any suggestions for changes.
`private_*'
The DBI provides a way to store extra information in a
DBI handle as "private" attributes. The DBI will allow
you to store and retreive any attribute which has a
name starting with "`private_'". It is strongly recom
mended that you use just one private attribute (e.g.,
use a hash ref) and give it a long and unambiguous
name that includes the module or application name that
the attribute relates to (e.g., "`private_YourFullMod
uleName_thingy'").
DBI DATABASE HANDLE OBJECTS
This section covers the methods and attributes associated
with database handles.
Database Handle Methods
The following methods are specified for DBI database han
dles:
`do'
$rc = $dbh->do($statement) or die $dbh->errstr;
$rc = $dbh->do($statement, \%attr) or die $dbh->errstr;
$rv = $dbh->do($statement, \%attr, @bind_values) or ...
Prepare and execute a single statement. Returns the
number of rows affected or `undef' on error. A return
value of `-1' means the number of rows is not known or
is not available.
This method is typically most useful for non-`SELECT'
statements that either cannot be prepared in advance
(due to a limitation of the driver) or do not need to
be executed repeatedly. It should not be used for
`SELECT' statements because it does not return a
statement handle (so you can't fetch any data).
The default `do' method is logically similar to:
sub do {
my($dbh, $statement, $attr, @bind_values) = @_;
my $sth = $dbh->prepare($statement, $attr) or return undef;
$sth->execute(@bind_values) or return undef;
my $rows = $sth->rows;
($rows == 0) ? "0E0" : $rows; # always return true if no error
}
For example:
DELETE FROM table
WHERE status = ?
}, undef, 'DONE') or die $dbh->errstr;
Using placeholders and `@bind_values' with the `do'
method can be useful because it avoids the need to
correctly quote any variables in the `$statement'. But
if you'll be executing the statement many times then
it's more efficient to `prepare' it once and call
`execute' many times instead.
The `q{...}' style quoting used in this example avoids
clashing with quotes that may be used in the SQL
statement. Use the double-quote-like `qq{...}' opera
tor if you want to interpolate variables into the
string. See the Quote and Quote-like Operators entry
in the perlop manpage for more details.
`selectrow_array'
@row_ary = $dbh->selectrow_array($statement);
@row_ary = $dbh->selectrow_array($statement, \%attr);
@row_ary = $dbh->selectrow_array($statement, \%attr, @bind_values);
This utility method combines the prepare, execute, and
fetchrow_array entries elsewhere in this document into
a single call. If called in a list context, it returns
the first row of data from the statement. If called in
a scalar context, it returns the first field of the
first row. The `$statement' parameter can be a previ
ously prepared statement handle, in which case the
`prepare' is skipped.
If any method fails, and the RaiseError entry else
where in this document is not set, `selectrow_array'
will return an empty list.
In a scalar context, `selectrow_array' returns the
value of the first field. An `undef' is returned if
there are no matching rows or an error occurred. Since
that `undef' can't be distinguished from an `undef'
returned because the first field value was NULL, call
ing `selectrow_array' in a scalar context should be
used with caution.
`selectall_arrayref'
$ary_ref = $dbh->selectall_arrayref($statement);
$ary_ref = $dbh->selectall_arrayref($statement, \%attr);
$ary_ref = $dbh->selectall_arrayref($statement, \%attr, @bind_values);
This utility method combines the prepare, execute, and
fetchall_arrayref entries elsewhere in this document
into a single call. It returns a reference to an array
containing a reference to an array for each row of
The `$statement' parameter can be a previously pre
pared statement handle, in which case the `prepare' is
skipped. This is recommended if the statement is going
to be executed many times.
If the RaiseError entry elsewhere in this document is
not set and any method except `fetchall_arrayref'
fails then `selectall_arrayref' will return `undef';
if `fetchall_arrayref' fails then it will return with
whatever data it has been fetched thus far. $DBI::err
should be checked to catch that.
`selectall_hashref'
$ary_ref = $dbh->selectall_hashref($statement);
$ary_ref = $dbh->selectall_hashref($statement, \%attr);
$ary_ref = $dbh->selectall_hashref($statement, \%attr, @bind_values);
This utility method combines the prepare, execute, and
fetchrow_hashref entries elsewhere in this document
into a single call. It returns a reference to an array
containing, for each row of data fetched, a reference
to a hash containing field name and value pairs for
that row.
The `$statement' parameter can be a previously pre
pared statement handle, in which case the `prepare' is
skipped. This is recommended if the statement is going
to be executed many times.
If any method except `fetchrow_hashref' fails, and the
RaiseError entry elsewhere in this document is not
set, `selectall_hashref' will return `undef'. If
`fetchrow_hashref' fails and the RaiseError entry
elsewhere in this document is not set, then it will
return with whatever data it has fetched thus far.
$DBI::err should be checked to catch that.
`selectcol_arrayref'
$ary_ref = $dbh->selectcol_arrayref($statement);
$ary_ref = $dbh->selectcol_arrayref($statement, \%attr);
$ary_ref = $dbh->selectcol_arrayref($statement, \%attr, @bind_values);
This utility method combines the prepareand execute
entries elsewhere in this document, and fetching one
column from all the rows, into a single call. It
returns a reference to an array containing the values
of the first column from each row.
The `$statement' parameter can be a previously pre
pared statement handle, in which case the `prepare' is
skipped. This is recommended if the statement is going
to be executed many times.
entry elsewhere in this document is not set, `select
col_arrayref' will return `undef'. If `fetch' fails
and the RaiseError entry elsewhere in this document is
not set, then it will return with whatever data it has
fetched thus far. $DBI::err should be checked to catch
that.
`prepare'
$sth = $dbh->prepare($statement) or die $dbh->errstr;
$sth = $dbh->prepare($statement, \%attr) or die $dbh->errstr;
Prepares a single statement for later execution by the
database engine and returns a reference to a statement
handle object.
The returned statement handle can be used to get
attributes of the statement and invoke the the execute
entry elsewhere in this document method. See the
Statement Handle Methods entry elsewhere in this docu
ment.
Drivers for engines without the concept of preparing a
statement will typically just store the statement in
the returned handle and process it when `$sth-'>`exe
cute' is called. Such drivers are unlikely to give
much useful information about the statement, such as
`$sth-'>`{NUM_OF_FIELDS}', until after `$sth-'>`exe
cute' has been called. Portable applications should
take this into account.
In general, DBI drivers do not parse the contents of
the statement (other than simply counting any the
Placeholders entry elsewhere in this document). The
statement is passed directly to the database engine,
sometimes known as pass-thru mode. This has advantages
and disadvantages. On the plus side, you can access
all the functionality of the engine being used. On the
downside, you're limited if you're using a simple
engine, and you need to take extra care if writing
applications intended to be portable between engines.
Portable applications should not assume that a new
statement can be prepared and/or executed while still
fetching results from a previous statement.
Some command-line SQL tools use statement terminators,
like a semicolon, to indicate the end of a statement.
Such terminators should not normally be used with the
DBI.
`prepare_cached'
$sth = $dbh->prepare_cached($statement, \%attr)
$sth = $dbh->prepare_cached($statement, \%attr, $allow_active)
Like the prepare entry elsewhere in this document
except that the statement handle returned will be
stored in a hash associated with the `$dbh'. If
another call is made to `prepare_cached' with the same
`$statement' and `%attr' values, then the correspond
ing cached `$sth' will be returned without contacting
the database server.
This caching can be useful in some applications, but
it can also cause problems and should be used with
care. If the cached `$sth' being returned is active
(i.e., is a `SELECT' that may still have data to be
fetched) then a warning will be generated and `finish'
will be called for you. The warning can be suppressed
by setting `$allow_active' to true. The cache can be
accessed (and cleared) via the the CachedKids entry
elsewhere in this document attribute.
Here's an example of one possible use of `pre
pare_cached':
while ( ($field, $value) = each %search_fields ) {
push @sql, "$field = ?";
push @values, $value;
}
$qualifier = "";
$qualifier = "where ".join(" and ", @sql) if @sql;
$sth = $dbh->prepare_cached("SELECT * FROM table $qualifier");
$sth->execute(@values);
`commit'
$rc = $dbh->commit or die $dbh->errstr;
Commit (make permanent) the most recent series of
database changes if the database supports transactions
and AutoCommit is off.
If `AutoCommit' is on, then calling `commit' will
issue a "commit ineffective with AutoCommit" warning.
See also the Transactions entry elsewhere in this doc
ument in the the FURTHER INFORMATION entry elsewhere
in this document section below.
`rollback'
$rc = $dbh->rollback or die $dbh->errstr;
Rollback (undo) the most recent series of uncommitted
database changes if the database supports transactions
If `AutoCommit' is on, then calling `rollback' will
issue a "rollback ineffective with AutoCommit" warn
ing.
See also the Transactions entry elsewhere in this doc
ument in the the FURTHER INFORMATION entry elsewhere
in this document section below.
`disconnect'
$rc = $dbh->disconnect or warn $dbh->errstr;
Disconnects the database from the database handle.
`disconnect' is typically only used before exiting the
program. The handle is of little use after disconnect
ing.
The transaction behavior of the `disconnect' method
is, sadly, undefined. Some database systems (such as
Oracle and Ingres) will automatically commit any out
standing changes, but others (such as Informix) will
rollback any outstanding changes. Applications not
using `AutoCommit' should explicitly call `commit' or
`rollback' before calling `disconnect'.
The database is automatically disconnected by the
`DESTROY' method if still connected when there are no
longer any references to the handle. The `DESTROY'
method for each driver should implicitly call `roll
back' to undo any uncommitted changes. This is vital
behavior to ensure that incomplete transactions don't
get committed simply because Perl calls `DESTROY' on
every object before exiting. Also, do not rely on the
order of object destruction during "global destruc
tion", as it is undefined.
Generally, if you want your changes to be commited or
rolled back when you disconnect, then you should
explicitly call the commit entry elsewhere in this
document or the rollback entry elsewhere in this docu
ment before disconnecting.
If you disconnect from a database while you still have
active statement handles, you will get a warning. The
statement handles should either be cleared (destroyed)
before disconnecting, or the `finish' method should be
called on each one.
`ping'
$rc = $dbh->ping;
Attempts to determine, in a reasonably efficient way,
if the database server is still running and the
should implement this function in the most suitable
manner for their database engine.
The current default implementation always returns true
without actually doing anything. Actually, it returns
"`0 but true'" which is true but zero. That way you
can tell if the return value is genuine or just the
default. Drivers should override this method with one
that does the right thing for their type of database.
Few applications would have direct use for this
method. See the specialized Apache::DBI module for one
example usage.
`table_info' NEW
Warning: This method is experimental and may change.
$sth = $dbh->table_info;
$sth = $dbh->table_info( \%attr );
Returns an active statement handle that can be used to
fetch information about tables and views that exist in
the database.
The following attributes (all or separate) may be used
as selection criteria:
%attr = (
TABLE_CAT => $CatVal # String value of the catalog name
, TABLE_SCHEM => $SchVal # String value of the schema name
, TABLE_NAME => $TblVal # String value of the table name
, TABLE_TYPE => $TypVal # String value of the table type(s)
);
Note: The support for the selection criteria is driver
specific. If the driver doesn't support one or more
then them then you'll get back more than you asked for
and can do the filtering yourself.
The arguments TABLE_CAT, TABLE_SCHEM and TABLE_NAME
may accept search patterns according to the
database/driver, for example:
$sth = $dbh->table_info( { TABLE_NAME => '%TAB%'} );
The value of TABLE_TYPE is a comma-separated list of
one or more types of tables to be returned in the
result set. Each value may optionally be quoted, e.g.:
$sth = $dbh->table_info( { TABLE_TYPE => "TABLE" } );
$sth = $dbh->table_info( { TABLE_TYPE => "'TABLE', 'VIEW'" } );
In addition the following special cases may also be
· If the value of TABLE_CAT is '%' and TABLE_SCHEM and
TABLE_NAME name are empty strings, the result set
contains a list of catalog names. For example:
$sth = $dbh->table_info({ TABLE_CAT=>'%', TABLE_SCHEM=>'', TABLE_NAME=>'' });
· If the value of TABLE_SCHEM is '%' and TABLE_CAT and
TABLE_NAME are empty strings, the result set
contains a list of schema names.
· If the value of TABLE_TYPE is '%' and TABLE_CAT,
TABLE_SCHEM, and TABLE_NAME are all empty strings,
the result set contains a list of table types.
The statement handle returned has at least the follow
ing fields in the order show below. Other fields,
after these, may also be present.
TABLE_CAT: Table catalog identifier. This field is
NULL (`undef') if not applicable to the data source,
which is usually the case. This field is empty if not
applicable to the table.
TABLE_SCHEM: The name of the schema containing the
TABLE_NAME value. This field is NULL (`undef') if not
applicable to data source, and empty if not applicable
to the table.
TABLE_NAME: Name of the table (or view, synonym, etc).
TABLE_TYPE: One of the following: "TABLE", "VIEW",
"SYSTEM TABLE", "GLOBAL TEMPORARY", "LOCAL TEMPORARY",
"ALIAS", "SYNONYM" or a type identifier that is spe
cific to the data source.
REMARKS: A description of the table. May be NULL
(`undef').
Note that `table_info' might not return records for
all tables. Applications can use any valid table
regardless of whether it's returned by `table_info'.
See also the tables entry elsewhere in this document.
For more detailed information about the fields and
their meanings, you can refer to:
http://msdn.microsoft.com/library/psdk/dasdk/odch6wqb.htm
If that URL ceases to work then use the MSDN search
facility at:
http://search.microsoft.com/us/dev/
phrase option. The link you want will probably just
be called `SQLTables' and will be part of the Data
Access SDK.
See also page 306 of the (very large) SQL/CLI specifi
cation:
http://www.jtc1sc32.org/sc32/jtc1sc32.nsf/Attachments/DF86E81BE70151D58525699800643F56/$FILE/32N0595T.PDF
`tables' NEW
Warning: This method is experimental and may change.
@names = $dbh->tables;
@names = $dbh->tables( \%attr );
Returns a list of table and view names, possibly
including a schema prefix. This list should include
all tables that can be used in a `SELECT' statement
without further qualification.
Note that `table_info' might not return records for
all tables. Applications can use any valid table
regardless of whether it's returned by tables. See
also the table_info entry elsewhere in this document.
`type_info_all' NEW
Warning: This method is experimental and may change.
$type_info_all = $dbh->type_info_all;
Returns a reference to an array which holds informa
tion about each data type variant supported by the
database and driver. The array and its contents should
be treated as read-only.
The first item is a reference to an 'index' hash of
`Name ='> `Index' pairs. The items following that are
references to arrays, one per supported data type
variant. The leading index hash defines the names and
order of the fields within the arrays that follow it.
For example:
{ TYPE_NAME => 0,
DATA_TYPE => 1,
COLUMN_SIZE => 2, # was PRECISION originally
LITERAL_PREFIX => 3,
LITERAL_SUFFIX => 4,
CREATE_PARAMS => 5,
NULLABLE => 6,
CASE_SENSITIVE => 7,
SEARCHABLE => 8,
UNSIGNED_ATTRIBUTE=> 9,
FIXED_PREC_SCALE => 10, # was MONEY originally
AUTO_UNIQUE_VALUE => 11, # was AUTO_INCREMENT originally
LOCAL_TYPE_NAME => 12,
MINIMUM_SCALE => 13,
MAXIMUM_SCALE => 14,
NUM_PREC_RADIX => 15,
},
[ 'VARCHAR', SQL_VARCHAR,
undef, "'","'", undef,0, 1,1,0,0,0,undef,1,255, undef
],
[ 'INTEGER', SQL_INTEGER,
undef, "", "", undef,0, 0,1,0,0,0,undef,0, 0, 10
],
];
Note that more than one row may have the same value in
the `DATA_TYPE' field if there are different ways to
spell the type name and/or there are variants of the
type with different attributes (e.g., with and without
`AUTO_UNIQUE_VALUE' set, with and without
`UNSIGNED_ATTRIBUTE', etc).
The rows are ordered by `DATA_TYPE' first and then by
how closely each type maps to the corresponding ODBC
SQL data type, closest first.
The meaning of the fields is described in the documen
tation for the the type_info entry elsewhere in this
document method. The index values shown above (e.g.,
`NULLABLE ='> `6') are for illustration only. Drivers
may define the fields with a different order.
This method is not normally used directly. The the
type_info entry elsewhere in this document method pro
vides a more useful interface to the data.
Even though an 'index' hash is provided, all the field
names in the index hash defined above will always have
the index values defined above. This is defined
behaviour so that you don't need to rely on the index
hash, which is handy because the lettercase of the
keys is not defined. It is usually uppercase, as show
here, but drivers are free to return names with any
driver-specific columns of information - though it's
recommended that they start at column index 50 to
leave room for expansion of the DBI/ODBC specifica
tion.
`type_info' NEW
Warning: This method is experimental and may change.
@type_info = $dbh->type_info($data_type);
Returns a list of hash references holding information
about one or more variants of `$data_type'. The list
is ordered by `DATA_TYPE' first and then by how
closely each type maps to the corresponding ODBC SQL
data type, closest first. If called in a scalar con
text then only the first (best) element is returned.
If `$data_type' is undefined or `SQL_ALL_TYPES', then
the list will contain hashes for all data type vari
ants supported by the database and driver.
If `$data_type' is an array reference then `type_info'
returns the information for the first type in the
array that has any matches.
The keys of the hash follow the same letter case con
ventions as the rest of the DBI (see the Naming Con
ventions and Name Space entry elsewhere in this docu
ment). The following items should exist:
TYPE_NAME (string)
Data type name for use in CREATE TABLE statements
etc.
DATA_TYPE (integer)
SQL data type number.
COLUMN_SIZE (integer)
For numeric types, this is either the total number
of digits (if the NUM_PREC_RADIX value is 10) or
the total number of bits allowed in the column (if
NUM_PREC_RADIX is 2).
For string types, this is the maximum size of the
string in bytes.
For date and interval types, this is the maximum
number of characters needed to display the value.
LITERAL_PREFIX (string)
Characters used to prefix a literal. A typical
prefix is "`''" for characters, or possibly "`0x'"
for binary values passed as hexadecimal. NULL
this is not applicable.
LITERAL_SUFFIX (string)
Characters used to suffix a literal. Typically
"`''" for characters. NULL (`undef') is returned
for data types where this is not applicable.
CREATE_PARAMS (string)
Parameter names for data type definition. For
example, `CREATE_PARAMS' for a `DECIMAL' would be
"`precision,scale'" if the DECIMAL type should be
declared as `DECIMAL('precision,scale`)' where
precision and scale are integer values. For a
`VARCHAR' it would be "`max length'". NULL
(`undef') is returned for data types for which
this is not applicable.
NULLABLE (integer)
Indicates whether the data type accepts a NULL
value: `0' or an empty string = no, `1' = yes, `2'
= unknown.
CASE_SENSITIVE (boolean)
Indicates whether the data type is case sensitive
in collations and comparisons.
SEARCHABLE (integer)
Indicates how the data type can be used in a WHERE
clause, as follows:
0 - Cannot be used in a WHERE clause
1 - Only with a LIKE predicate
2 - All comparison operators except LIKE
3 - Can be used in a WHERE clause with any comparison operator
UNSIGNED_ATTRIBUTE (boolean)
Indicates whether the data type is unsigned. NULL
(`undef') is returned for data types for which
this is not applicable.
FIXED_PREC_SCALE (boolean)
Indicates whether the data type always has the
same precision and scale (such as a money type).
NULL (`undef') is returned for data types for
which this is not applicable.
AUTO_UNIQUE_VALUE (boolean)
Indicates whether a column of this data type is
automatically set to a unique value whenever a new
row is inserted. NULL (`undef') is returned for
data types for which this is not applicable.
Localized version of the `TYPE_NAME' for use in
dialog with users. NULL (`undef') is returned if
a localized name is not available (in which case
`TYPE_NAME' should be used).
MINIMUM_SCALE (integer)
The minimum scale of the data type. If a data type
has a fixed scale, then `MAXIMUM_SCALE' holds the
same value. NULL (`undef') is returned for data
types for which this is not applicable.
MAXIMUM_SCALE (integer)
The maximum scale of the data type. If a data type
has a fixed scale, then `MINIMUM_SCALE' holds the
same value. NULL (`undef') is returned for data
types for which this is not applicable.
SQL_DATA_TYPE (integer)
This column is the same as the `DATA_TYPE' column,
except for interval and datetime data types. For
interval and datetime data types, the
`SQL_DATA_TYPE' field will return `SQL_INTERVAL'
or `SQL_DATETIME', and the `SQL_DATETIME_SUB'
field below will return the subcode for the spe
cific interval or datetime data type. If this
field is NULL, then the driver does not support or
report on interval or date subtypes.
SQL_DATETIME_SUB (integer)
For interval or datetime data types, where the
`SQL_DATA_TYPE' field above is `SQL_INTERVAL' or
`SQL_DATETIME', this field will hold the subcode
for the specific interval or datetime data type.
Otherwise it will be NULL (`undef').
NUM_PREC_RADIX (integer)
The radix value of the data type. For approximate
numeric types, `NUM_PREC_RADIX' contains the value
2 and `COLUMN_SIZE' holds the number of bits. For
exact numeric types, `NUM_PREC_RADIX' contains the
value 10 and `COLUMN_SIZE' holds the number of
decimal digits. NULL (`undef') is returned either
for data types for which this is not applicable or
if the driver cannot report this information.
INTERVAL_PRECISION (integer)
The interval leading precision for interval types.
NULL is returned either for data types for which
this is not applicable or if the driver cannot
report this information.
For example, to find the type name for the fields in a
select statement you can do:
Since DBI and ODBC drivers vary in how they map their
types into the ISO standard types you may need to
search for more than one type. Here's an example
looking for a usable type to store a date:
$my_date_type = $dbh->type_info( [ SQL_DATE, SQL_TIMESTAMP ] );
Similarly, to more reliably find a type to store small
integers, you could use a list starting with
`SQL_SMALLINT', `SQL_INTEGER', `SQL_DECIMAL', etc.
For more detailed information about these fields and
their meanings, you can refer to:
http://msdn.microsoft.com/library/psdk/dasdk/odch6yy7.htm
If that URL ceases to work then use the MSDN search
facility at
http://search.microsoft.com/us/dev/
and search the MSDN Library for `SQLGetTypeInfo
returns' using the exact phrase option. The link you
want will probably just be called `SQLGetTypeInfo'
(there may be more than one).
The individual data types are currently described
here:
http://msdn.microsoft.com/library/psdk/dasdk/odap8fcj.htm
If that URL ceases to work, or to get more general
information, use the MSDN search facility as described
above and search for `SQL Data Types'.
`quote'
$sql = $dbh->quote($value);
$sql = $dbh->quote($value, $data_type);
Quote a string literal for use as a literal value in
an SQL statement, by escaping any special characters
(such as quotation marks) contained within the string
and adding the required type of outer quotation marks.
$sql = sprintf "SELECT foo FROM bar WHERE baz = %s",
$dbh->quote("Don't");
For most database types, quote would return `'Don''t''
(including the outer quotation marks).
An undefined `$value' value will be returned as the
string `NULL' (without quotation marks) to match how
If `$data_type' is supplied, it is used to try to
determine the required quoting behavior by using the
information returned by the type_info entry elsewhere
in this document. As a special case, the standard
numeric types are optimized to return `$value' without
calling `type_info'.
Quote will probably not be able to deal with all pos
sible input (such as binary data or data containing
newlines), and is not related in any way with escaping
or quoting shell meta-characters. There is no need to
quote values being used with the Placeholders and Bind
Values entry elsewhere in this document.
Database Handle Attributes
This section describes attributes specific to database
handles.
Changes to these database handle attributes do not affect
any other existing or future database handles.
Attempting to set or get the value of an unknown attribute
is fatal, except for private driver-specific attributes
(which all have names starting with a lowercase letter).
Example:
$h->{AutoCommit} = ...; # set/write
... = $h->{AutoCommit}; # get/read
`AutoCommit' (boolean)
If true, then database changes cannot be rolled-back
(undone). If false, then database changes automati
cally occur within a "transaction", which must either
be committed or rolled back using the `commit' or
`rollback' methods.
Drivers should always default to `AutoCommit' mode (an
unfortunate choice largely forced on the DBI by ODBC
and JDBC conventions.)
Attempting to set `AutoCommit' to an unsupported value
is a fatal error. This is an important feature of the
DBI. Applications that need full transaction behavior
can set `$dbh-'>`{AutoCommit} = 0' (or set `AutoCom
mit' to 0 via the connect entry elsewhere in this doc
ument) without having to check that the value was
assigned successfully.
For the purposes of this description, we can divide
Databases which don't support transactions at all.
Databases in which a transaction is always active.
Databases in which a transaction must be explicitly started (C<'BEGIN WORK'>).
* Databases which don't support transactions at all
For these databases, attempting to turn `AutoCommit'
off is a fatal error. `commit' and `rollback' both
issue warnings about being ineffective while `AutoCom
mit' is in effect.
* Databases in which a transaction is always active
These are typically mainstream commercial relational
databases with "ANSI standard" transaction behavior.
If `AutoCommit' is off, then changes to the database
won't have any lasting effect unless the commit entry
elsewhere in this document is called (but see also the
disconnect entry elsewhere in this document). If the
rollback entry elsewhere in this document is called
then any changes since the last commit are undone.
If `AutoCommit' is on, then the effect is the same as
if the DBI called `commit' automatically after every
successful database operation. In other words, calling
`commit' or `rollback' explicitly while `AutoCommit'
is on would be ineffective because the changes would
have already been commited.
Changing `AutoCommit' from off to on should issue a
the commit entry elsewhere in this document in most
drivers.
Changing `AutoCommit' from on to off should have no
immediate effect.
For databases which don't support a specific auto-com
mit mode, the driver has to commit each statement
automatically using an explicit `COMMIT' after it com
pletes successfully (and roll it back using an
explicit `ROLLBACK' if it fails). The error informa
tion reported to the application will correspond to
the statement which was executed, unless it succeeded
and the commit or rollback failed.
* Databases in which a transaction must be explicitly
started
For these databases, the intention is to have them act
like databases in which a transaction is always active
(as described above).
transaction when `AutoCommit' is turned off (from the
default "on" state) and will automatically begin
another transaction after a the commit entry elsewhere
in this document or the rollback entry elsewhere in
this document. In this way, the application does not
have to treat these databases as a special case.
See the commit, disconnect, and Transactions entries
elsewhere in this document for other important notes
about transactions.
`Driver' (handle)
Holds the handle of the parent driver. The only recom
mended use for this is to find the name of the driver
using:
$dbh->{Driver}->{Name}
`Name' (string)
Holds the "name" of the database. Usually (and recom
mended to be) the same as the "`dbi:DriverName:...'"
string used to connect to the database, but with the
leading "`dbi:DriverName:'" removed.
`Statement' (string, read-only)
Returns the statement string passed to the most recent
the prepare entry elsewhere in this document method
called in this database handle, even if that method
failed. This is especially useful where `RaiseError'
is enabled and the exception handler checks $@ and
sees that a 'prepare' method call failed.
`RowCacheSize' (integer)
A hint to the driver indicating the size of the local
row cache that the application would like the driver
to use for future `SELECT' statements. If a row cache
is not implemented, then setting `RowCacheSize' is
ignored and getting the value returns `undef'.
Some `RowCacheSize' values have special meaning, as
follows:
0 - Automatically determine a reasonable cache size for each C<SELECT>
1 - Disable the local row cache
>1 - Cache this many rows
<0 - Cache as many rows that will fit into this much memory for each C<SELECT>.
Note that large cache sizes may require a very large
amount of memory (cached rows * maximum size of row).
Also, a large cache will cause a longer delay not only
for the first fetch, but also whenever the cache needs
refilling.
document statement handle attribute.
DBI STATEMENT HANDLE OBJECTS
This section lists the methods and attributes associated
with DBI statement handles.
Statement Handle Methods
The DBI defines the following methods for use on DBI
statement handles:
`bind_param'
$rc = $sth->bind_param($p_num, $bind_value) or die $sth->errstr;
$rv = $sth->bind_param($p_num, $bind_value, \%attr) or ...
$rv = $sth->bind_param($p_num, $bind_value, $bind_type) or ...
The `bind_param' method can be used to bind a value
with a placeholder embedded in the prepared statement.
Placeholders are indicated with question mark charac
ter (`?'). For example:
$dbh->{RaiseError} = 1; # save having to check each method call
$sth = $dbh->prepare("SELECT name, age FROM people WHERE name LIKE ?");
$sth->bind_param(1, "John%"); # placeholders are numbered from 1
$sth->execute;
DBI::dump_results($sth);
Note that the `?' is not enclosed in quotation marks,
even when the placeholder represents a string. Some
drivers also allow placeholders like `:'name and `:'n
(e.g., `:1', `:2', and so on) in addition to `?', but
their use is not portable. Undefined bind values or
`undef' can be used to indicate null values.
Some drivers do not support placeholders.
With most drivers, placeholders can't be used for any
element of a statement that would prevent the database
server from validating the statement and creating a
query execution plan for it. For example:
"SELECT name, age FROM ?" # wrong (will probably fail)
"SELECT name, ? FROM people" # wrong (but may not 'fail')
Also, placeholders can only represent single scalar
values. For example, the following statement won't
work as expected for more than one value:
"SELECT name, age FROM people WHERE name IN (?)" # wrong
Data Types for Placeholders
The `\%attr' parameter can be used to hint at the data
driver is only interested in knowing if the place
holder should be bound as a number or a string.
$sth->bind_param(1, $value, { TYPE => SQL_INTEGER });
As a short-cut for this common case, the data type can
be passed directly, in place of the `\%attr' hash ref
erence. This example is equivalent to the one above:
$sth->bind_param(1, $value, SQL_INTEGER);
The `TYPE' value indicates the standard (non-driver-
specific) type for this parameter. To specify the
driver-specific type, the driver may support a driver-
specific attribute, such as `{ ora_type ='>` 97 }'.
The data type for a placeholder cannot be changed
after the first `bind_param' call. However, it can be
left unspecified, in which case it defaults to the
previous value.
The SQL_INTEGER and other related constants can be
imported using
use DBI qw(:sql_types);
See the DBI Constants entry elsewhere in this document
for more information.
Perl only has string and number scalar data types. All
database types that aren't numbers are bound as
strings and must be in a format the database will
understand.
As an alternative to specifying the data type in the
`bind_param' call, you can let the driver pass the
value as the default type (`VARCHAR'). You can then
use an SQL function to convert the type within the
statement. For example:
INSERT INTO price(code, price) VALUES (?, CONVERT(MONEY,?))
The `CONVERT' function used here is just an example.
The actual function and syntax will vary between dif
ferent databases and is non-portable.
See also the Placeholders and Bind Values entry else
where in this document for more information.
`bind_param_inout'
$rc = $sth->bind_param_inout($p_num, \$bind_value, $max_len) or die $sth->errstr;
$rv = $sth->bind_param_inout($p_num, \$bind_value, $max_len, \%attr) or ...
$rv = $sth->bind_param_inout($p_num, \$bind_value, $max_len, $bind_type) or ...
in this document, but also enables values to be
updated by the statement. The statement is typically a
call to a stored procedure. The `$bind_value' must be
passed as a reference to the actual value to be used.
Note that unlike the bind_param entry elsewhere in
this document, the `$bind_value' variable is not read
when `bind_param_inout' is called. Instead, the value
in the variable is read at the time the execute entry
elsewhere in this document is called.
The additional `$max_len' parameter specifies the min
imum amount of memory to allocate to `$bind_value' for
the new value. If the value returned from the database
is too big to fit, then the execution should fail. If
unsure what value to use, pick a generous length,
i.e., a length larger than the longest value that
would ever be returned. The only cost of using a
larger value than needed is wasted memory.
It is expected that few drivers will support this
method. The only driver currently known to do so is
DBD::Oracle (DBD::ODBC may support it in a future
release). Therefore it should not be used for database
independent applications.
Undefined values or `undef' are used to indicate null
values. See also the Placeholders and Bind Values
entry elsewhere in this document for more information.
`execute'
$rv = $sth->execute or die $sth->errstr;
$rv = $sth->execute(@bind_values) or die $sth->errstr;
Perform whatever processing is necessary to execute
the prepared statement. An `undef' is returned if an
error occurs. A successful `execute' always returns
true regardless of the number of rows affected, even
if it's zero (see below). It is always important to
check the return status of `execute' (and most other
DBI methods) for errors.
For a non-`SELECT' statement, `execute' returns the
number of rows affected, if known. If no rows were
affected, then `execute' returns "`0E0'", which Perl
will treat as 0 but will regard as true. Note that it
is not an error for no rows to be affected by a state
ment. If the number of rows affected is not known,
then `execute' returns -1.
For `SELECT' statements, execute simply "starts" the
query within the database engine. Use one of the fetch
methods to retreive the data after calling `execute'.
rows that will be returned by the query (because most
databases can't tell in advance), it simply returns a
true value.
If any arguments are given, then `execute' will effec
tively call the bind_param entry elsewhere in this
document for each value before executing the state
ment. Values bound in this way are usually treated as
`SQL_VARCHAR' types unless the driver can determine
the correct type (which is rare), or unless
`bind_param' (or `bind_param_inout') has already been
used to specify the type.
`fetchrow_arrayref'
$ary_ref = $sth->fetchrow_arrayref;
$ary_ref = $sth->fetch; # alias
Fetches the next row of data and returns a reference
to an array holding the field values. Null fields are
returned as `undef' values in the array. This is the
fastest way to fetch data, particularly if used with
`$sth-'>`bind_columns'.
If there are no more rows or if an error occurs, then
`fetchrow_arrayref' returns an `undef'. You should
check `$sth-'>`err' afterwards (or use the `RaiseEr
ror' attribute) to discover if the `undef' returned
was due to an error.
Note that the same array reference is returned for
each fetch, so don't store the reference and then use
it after a later fetch. Also, the elements of the
array are also reused for each row, so take care if
you want to take a reference to an element. See also
the bind_columns entry elsewhere in this document.
`fetchrow_array'
@ary = $sth->fetchrow_array;
An alternative to `fetchrow_arrayref'. Fetches the
next row of data and returns it as a list containing
the field values. Null fields are returned as `undef'
values in the list.
If there are no more rows or if an error occurs, then
`fetchrow_array' returns an empty list. You should
check `$sth-'>`err' afterwards (or use the `RaiseEr
ror' attribute) to discover if the empty list returned
was due to an error.
In a scalar context, `fetchrow_array' returns the
value of the first field. An `undef' is returned if
there are no more rows or if an error occurred. Since
returned because the first field value was NULL, you
should exercise some caution if you use
`fetchrow_array' in a scalar context.
`fetchrow_hashref'
$hash_ref = $sth->fetchrow_hashref;
$hash_ref = $sth->fetchrow_hashref($name);
An alternative to `fetchrow_arrayref'. Fetches the
next row of data and returns it as a reference to a
hash containing field name and field value pairs.
Null fields are returned as `undef' values in the
hash.
If there are no more rows or if an error occurs, then
`fetchrow_hashref' returns an `undef'. You should
check `$sth-'>`err' afterwards (or use the `RaiseEr
ror' attribute) to discover if the `undef' returned
was due to an error.
The optional `$name' parameter specifies the name of
the statement handle attribute. For historical reasons
it defaults to "`NAME'", however using either
"`NAME_lc'" or "`NAME_uc'" is recomended for portabil
ity.
The keys of the hash are the same names returned by
`$sth-'>`{$name}'. If more than one field has the same
name, there will only be one entry in the returned
hash for those fields.
Because of the extra work `fetchrow_hashref' and Perl
have to perform, it is not as efficient as
`fetchrow_arrayref' or `fetchrow_array'.
Currently, a new hash reference is returned for each
row. This will change in the future to return the
same hash ref each time, so don't rely on the current
behaviour.
`fetchall_arrayref'
$tbl_ary_ref = $sth->fetchall_arrayref;
$tbl_ary_ref = $sth->fetchall_arrayref( $slice_array_ref );
$tbl_ary_ref = $sth->fetchall_arrayref( $slice_hash_ref );
The `fetchall_arrayref' method can be used to fetch
all the data to be returned from a prepared and exe
cuted statement handle. It returns a reference to an
array that contains one reference per row.
If there are no rows to return, `fetchall_arrayref'
returns a reference to an empty array. If an error
occurs, `fetchall_arrayref' returns the data fetched
`$sth-'>`err' afterwards (or use the `RaiseError'
attribute) to discover if the data is complete or was
truncated due to an error.
When passed an array reference, `fetchall_arrayref'
uses the fetchrow_arrayref entry elsewhere in this
document to fetch each row as an array ref. If the
parameter array is not empty then it is used as a
slice to select individual columns by index number.
With no parameters, `fetchall_arrayref' acts as if
passed an empty array ref.
When passed a hash reference, `fetchall_arrayref' uses
the fetchrow_hashref entry elsewhere in this document
to fetch each row as a hash reference. If the parame
ter hash is empty then fetchrow_hashref is simply
called in a tight loop and the keys in the hashes have
whatever name lettercase is returned by default from
fetchrow_hashref.
If the parameter hash is not empty, then it is used as
a slice to select individual columns by name. The
names should be lower case regardless of the letter
case in `$sth-'>`{NAME}'. The values of the hash
should be set to 1.
For example, to fetch just the first column of every
row:
$tbl_ary_ref = $sth->fetchall_arrayref([0]);
To fetch the second to last and last column of every
row:
$tbl_ary_ref = $sth->fetchall_arrayref([-2,-1]);
To fetch all fields of every row as a hash ref:
$tbl_ary_ref = $sth->fetchall_arrayref({});
To fetch only the fields called "foo" and "bar" of
every row as a hash ref:
$tbl_ary_ref = $sth->fetchall_arrayref({ foo=>1, bar=>1 });
The first two examples return a reference to an array
of array refs. The last returns a reference to an
array of hash refs.
`fetchall_hashref'
$tbl_ary_ref = $sth->fetchall_hashref;
the data to be returned from a prepared and executed
statement handle. It returns a reference to an array
that contains one hash of field name and value pairs
per row.
If there are no rows to return, `fetchall_hashref'
returns a reference to an empty array. If an error
occurs, `fetchall_hashref' returns the data fetched
thus far, which may be none. You should check
`$sth-'>`err' afterwards (or use the `RaiseError'
attribute) to discover if the data is complete or was
truncated due to an error.
`finish'
$rc = $sth->finish;
Indicates that no more data will be fetched from this
statement handle before it is either executed again or
destroyed. The `finish' method is rarely needed, but
can sometimes be helpful in very specific situations
to allow the server to free up resources (such as sort
buffers).
When all the data has been fetched from a `SELECT'
statement, the driver should automatically call `fin
ish' for you. So you should not normally need to call
it explicitly.
Consider a query like:
SELECT foo FROM table WHERE bar=? ORDER BY foo
where you want to select just the first (smallest)
"foo" value from a very large table. When executed,
the database server will have to use temporary buffer
space to store the sorted rows. If, after executing
the handle and selecting one row, the handle won't be
re-executed for some time and won't be destroyed, the
`finish' method can be used to tell the server that
the buffer space can be freed.
Calling `finish' resets the the Active entry elsewhere
in this document attribute for the statement. It may
also make some statement handle attributes (such as
`NAME' and `TYPE') unavailable if they have not
already been accessed (and thus cached).
The `finish' method does not affect the transaction
status of the database connection. It has nothing to
do with transactions. It's mostly an internal "house
keeping" method that is rarely needed. There's no need
to call `finish' if you're about to destroy or re-exe
cute the statement handle. See also the disconnect
entry elsewhere in this document attribute.
The `finish' method should have been called `can
cel_select'.
`rows'
$rv = $sth->rows;
Returns the number of rows affected by the last row
affecting command, or -1 if the number of rows is not
known or not available.
Generally, you can only rely on a row count after a
non-`SELECT' `execute' (for some specific operations
like `UPDATE' and `DELETE'), or after fetching all the
rows of a `SELECT' statement.
For `SELECT' statements, it is generally not possible
to know how many rows will be returned except by
fetching them all. Some drivers will return the num
ber of rows the application has fetched so far, but
others may return -1 until all rows have been fetched.
So use of the `rows' method or `$DBI::rows' with
`SELECT' statements is not recommended.
One alternative method to get a row count for a
`SELECT' is to execute a "SELECT COUNT(*) FROM ..."
SQL statement with the same "..." as your query and
then fetch the row count from that.
`bind_col'
$rc = $sth->bind_col($column_number, \$var_to_bind);
Binds an output column (field) of a `SELECT' statement
to a Perl variable. See `bind_columns' below for an
example. Note that column numbers count up from 1.
Whenever a row is fetched from the database, the cor
responding Perl variable is automatically updated.
There is no need to fetch and assign the values manu
ally. The binding is performed at a very low level
using Perl aliasing so there is no extra copying tak
ing place. This makes using bound variables very
efficient.
For maximum portability between drivers, `bind_col'
should be called after `execute'. This restriction may
be removed in a later version of the DBI.
You do not need to bind output columns in order to
fetch data, but it can be useful for some applications
which need either maximum performance or greater clar
ity of code. The the bind_param entry elsewhere in
function for input variables.
`bind_columns'
$rc = $sth->bind_columns(@list_of_refs_to_vars_to_bind);
Calls the bind_col entry elsewhere in this document
for each column of the `SELECT' statement. The
`bind_columns' method will die if the number of refer
ences does not match the number of fields.
For maximum portability between drivers,
`bind_columns' should be called after `execute'.
For example:
$dbh->{RaiseError} = 1; # do this, or check every call for errors
$sth = $dbh->prepare(q{ SELECT region, sales FROM sales_by_region });
$sth->execute;
my ($region, $sales);
# Bind Perl variables to columns:
$rv = $sth->bind_columns(\$region, \$sales);
# you can also use Perl's \(...) syntax (see perlref docs):
# $sth->bind_columns(\($region, $sales));
# Column binding is the most efficient way to fetch data
while ($sth->fetch) {
print "$region: $sales\n";
}
For compatibility with old scripts, the first parame
ter will be ignored if it is `undef' or a hash refer
ence.
Here's a more fancy example that binds columns to the
values inside a hash (thanks to H.Merijn Brand):
$sth->execute;
my %row;
$sth->bind_columns( \( @row{ @{$sth->{NAME_lc} } } ));
while ($sth->fetch) {
print "$row{region}: $row{sales}\n";
}
`dump_results'
$rows = $sth->dump_results($maxlen, $lsep, $fsep, $fh);
Fetches all the rows from `$sth', calls
`DBI::neat_list' for each row, and prints the results
to `$fh' (defaults to `STDOUT') separated by `$lsep'
(default `"\n"'). `$fsep' defaults to `", "' and
This method is designed as a handy utility for proto
typing and testing queries. Since it uses the
neat_list entry elsewhere in this document to format
and edit the string for reading by humans, it is not
recomended for data transfer applications.
Statement Handle Attributes
This section describes attributes specific to statement
handles. Most of these attributes are read-only.
Changes to these statement handle attributes do not affect
any other existing or future statement handles.
Attempting to set or get the value of an unknown attribute
is fatal, except for private driver specific attributes
(which all have names starting with a lowercase letter).
Example:
... = $h->{NUM_OF_FIELDS}; # get/read
Note that some drivers cannot provide valid values for
some or all of these attributes until after `$sth-'>`exe
cute' has been called.
See also the finish entry elsewhere in this document to
learn more about the effect it may have on some
attributes.
`NUM_OF_FIELDS' (integer, read-only)
Number of fields (columns) the prepared statement will
return. Non-`SELECT' statements will have
`NUM_OF_FIELDS == 0'.
`NUM_OF_PARAMS' (integer, read-only)
The number of parameters (placeholders) in the pre
pared statement. See SUBSTITUTION VARIABLES below for
more details.
`NAME' (array-ref, read-only)
Returns a reference to an array of field names for
each column. The names may contain spaces but should
not be truncated or have any trailing space. Note that
the names have the letter case (upper, lower or mixed)
as returned by the driver being used. Portable appli
cations should use the NAME_lc entry elsewhere in this
document or the NAME_uc entry elsewhere in this docu
ment.
print "First column name: $sth->{NAME}->[0]\n";
Like the NAME entry elsewhere in this document but
always returns lowercase names.
`NAME_uc' (array-ref, read-only)
Like the NAME entry elsewhere in this document but
always returns uppercase names.
`TYPE' (array-ref, read-only)
Returns a reference to an array of integer values for
each column. The value indicates the data type of the
corresponding column.
The values correspond to the international standards
(ANSI X3.135 and ISO/IEC 9075) which, in general
terms, means ODBC. Driver-specific types that don't
exactly match standard types should generally return
the same values as an ODBC driver supplied by the mak
ers of the database. That might include private type
numbers in ranges the vendor has officially registered
with the ISO working group:
ftp://jerry.ece.umassd.edu/isowg3/dbl/SQL_Registry
Where there's no vendor-supplied ODBC driver to be
compatible with, the DBI driver can use type numbers
in the range that is now officially reserved for use
by the DBI: -9999 to -9000.
All possible values for `TYPE' should have at least
one entry in the output of the `type_info_all' method
(see the type_info_all entry elsewhere in this docu
ment).
`PRECISION' (array-ref, read-only)
Returns a reference to an array of integer values for
each column. For non-numeric columns, the value gen
erally refers to either the maximum length or the
defined length of the column. For numeric columns,
the value refers to the maximum number of significant
digits used by the data type (without considering a
sign character or decimal point). Note that for
floating point types (REAL, FLOAT, DOUBLE), the "dis
play size" can be up to 7 characters greater than the
precision. (for the sign + decimal point + the letter
E + a sign + 2 or 3 digits).
`SCALE' (array-ref, read-only)
Returns a reference to an array of integer values for
each column. NULL (`undef') values indicate columns
where scale is not applicable.
`NULLABLE' (array-ref, read-only)
Returns a reference to an array indicating the
values are `0' (or an empty string) = no, `1' = yes,
`2' = unknown.
print "First column may return NULL\n" if $sth->{NULLABLE}->[0];
`CursorName' (string, read-only)
Returns the name of the cursor associated with the
statement handle, if available. If not available or if
the database driver does not support the `"where cur
rent of ..."' SQL syntax, then it returns `undef'.
`Statement' (string, read-only)
Returns the statement string passed to the the prepare
entry elsewhere in this document method.
`RowsInCache' (integer, read-only)
If the driver supports a local row cache for `SELECT'
statements, then this attribute holds the number of
un-fetched rows in the cache. If the driver doesn't,
then it returns `undef'. Note that some drivers pre-
fetch rows on execute, whereas others wait till the
first fetch.
See also the the RowCacheSize entry elsewhere in this
document database handle attribute.
FURTHER INFORMATION
Transactions
Transactions are a fundamental part of any robust database
system. They protect against errors and database corrup
tion by ensuring that sets of related changes to the
database take place in atomic (indivisible, all-or-noth
ing) units.
This section applies to databases that support transac
tions and where `AutoCommit' is off. See the AutoCommit
entry elsewhere in this document for details of using
`AutoCommit' with various types of databases.
The recommended way to implement robust transactions in
Perl applications is to use `RaiseError' and
`eval { ... }' (which is very fast, unlike `eval "..."').
For example:
$dbh->{RaiseError} = 1;
eval {
foo(...) # do lots of work here
bar(...) # including inserts
baz(...) # and updates
$dbh->commit; # commit the changes if we get this far
};
if ($@) {
warn "Transaction aborted because $@";
$dbh->rollback; # undo the incomplete changes
# add other application on-error-clean-up code here
}
If the `RaiseError' attribute is not set, then DBI calls
would need to be manually checked for errors, typically
like this:
$h->method(@args) or die $h->errstr;
With `RaiseError' set, the DBI will automatically `die' if
any DBI method call on that handle (or a child handle)
fails, so you don't have to test the return value of each
method call. See the RaiseError entry elsewhere in this
document for more details.
A major advantage of the `eval' approach is that the
transaction will be properly rolled back if any code (not
just DBI calls) in the inner application dies for any rea
son. The major advantage of using the `$h-'>`{RaiseError}'
attribute is that all DBI calls will be checked automati
cally. Both techniques are strongly recommended.
After calling `commit' or `rollback' many drivers will not
let you fetch from a previously active `SELECT' statement
handle that's a child of the same database handle. A typi
cal way round this is to connect the the database twice
and use one connection for `SELECT' statements.
Handling BLOB / LONG / Memo Fields
Many databases support "blob" (binary large objects),
"long", or similar datatypes for holding very long strings
or large amounts of binary data in a single field. Some
databases support variable length long values over
2,000,000,000 bytes in length.
Since values of that size can't usually be held in memory,
and because databases can't usually know in advance the
length of the longest long that will be returned from a
`SELECT' statement (unlike other data types), some special
handling is required.
In this situation, the value of the `$h-'>`{LongReadLen}'
allocate when fetching such fields. The `$h-'>`{LongTrun
cOk}' attribute is used to determine how to behave if a
fetched value can't fit into the buffer.
When trying to insert long or binary values, placeholders
should be used since there are often limits on the maximum
size of an `INSERT' statement and the the quote entry
elsewhere in this document method generally can't cope
with binary data. See the Placeholders and Bind Values
entry elsewhere in this document.
Simple Examples
Here's a complete example program to select and fetch some
data:
my $dbh = DBI->connect("dbi:DriverName:db_name", $user, $password)
or die "Can't connect to $data_source: $DBI::errstr";
my $sth = $dbh->prepare( q{
SELECT name, phone
FROM mytelbook
}) or die "Can't prepare statement: $DBI::errstr";
my $rc = $sth->execute
or die "Can't execute statement: $DBI::errstr";
print "Query will return $sth->{NUM_OF_FIELDS} fields.\n\n";
print "Field names: @{ $sth->{NAME} }\n";
while (($name, $phone) = $sth->fetchrow_array) {
print "$name: $phone\n";
}
# check for problems which may have terminated the fetch early
die $sth->errstr if $sth->err;
$dbh->disconnect;
Here's a complete example program to insert some data from
a file. (This example uses `RaiseError' to avoid needing
to check each call).
my $dbh = DBI->connect("dbi:DriverName:db_name", $user, $password, {
RaiseError => 1, AutoCommit => 0
});
my $sth = $dbh->prepare( q{
INSERT INTO table (name, phone) VALUES (?, ?)
});
while (<FH>) {
chomp;
my ($name, $phone) = split /,/;
$sth->execute($name, $phone);
}
close FH;
$dbh->commit;
$dbh->disconnect;
Here's how to convert fetched NULLs (undefined values)
into empty strings:
while($row = $sth->fetchrow_arrayref) {
# this is a fast and simple way to deal with nulls:
foreach (@$row) { $_ = '' unless defined }
print "@$row\n";
}
The `q{...}' style quoting used in these examples avoids
clashing with quotes that may be used in the SQL state
ment. Use the double-quote like `qq{...}' operator if you
want to interpolate variables into the string. See the
Quote and Quote-like Operators entry in the perlop manpage
for more details.
Threads and Thread Safety
Perl versions 5.004_50 and later include optional experi
mental support for multiple threads on many platforms. If
the DBI is built using a Perl that has threads enabled
then it will use a per-driver mutex to ensure that only
one thread is with a driver at any one time. Please note
that support for threads in Perl is still experimental and
is known to have some significant problems. It's use is
not recommended.
Signal Handling and Canceling Operations
The first thing to say is that signal handling in Perl is
currently not safe. There is always a small risk of Perl
crashing and/or core dumping when, or after, handling a
signal. (The risk was reduced with 5.004_04 but is still
present.)
The two most common uses of signals in relation to the DBI
are for canceling operations when the user types Ctrl-C
(interrupt), and for implementing a timeout using
`alarm()' and `$SIG{ALRM}'.
To assist in implementing these operations, the DBI pro
vides a `cancel' method for statement handles. The `can
cel' method should abort the current operation and is
However, it must be stressed that: a) few drivers imple
ment this at the moment (the DBI provides a default method
that just returns `undef'); and b) even if implemented,
there is still a possibility that the statement handle,
and possibly the parent database handle, will not be
usable afterwards.
If `cancel' returns true, then it has successfully invoked
the database engine's own cancel function. If it returns
false, then `cancel' failed. If it returns `undef', then
the database engine does not have cancel implemented.
DEBUGGING
In addition to the the trace entry elsewhere in this docu
ment method, you can enable the same trace information by
setting the `DBI_TRACE' environment variable before start
ing Perl.
On Unix-like systems using a Bourne-like shell, you can do
this easily on the command line:
DBI_TRACE=2 perl your_test_script.pl
If `DBI_TRACE' is set to a non-numeric value, then it is
assumed to be a file name and the trace level will be set
to 2 with all trace output appended to that file. If the
name begins with a number followed by an equal sign (`='),
then the number and the equal sign are stripped off from
the name, and the number is used to set the trace level.
For example:
DBI_TRACE=1=dbitrace.log perl your_test_script.pl
See also the the trace entry elsewhere in this document
method.
It can sometimes be handy to compare trace files from two
different runs of the same script. However using a tool
like `diff' doesn't work well because the trace file is
full of object addresses that may differ each run. Here's
a handy little command to strip those out:
perl -pe 's/\b0x[\da-f]{6,}/0xNNNN/gi; s/\b[\da-f]{6,}/<long number>/gi'
WARNING AND ERROR MESSAGES
Fatal Errors
Can't call method ""prepare"" without a package or object
refer ence
The `$dbh' handle you're using to call `prepare' is
failed. You should always check the return status of
DBI methods, or use the the RaiseError entry elsewhere
in this document attribute.
Can't call method ""execute"" without a package or object
refer ence
The `$sth' handle you're using to call `execute' is
probably undefined because the preceeding `prepare'
failed. You should always check the return status of
DBI methods, or use the the RaiseError entry elsewhere
in this document attribute.
DBI/DBD internal version mismatch
The DBD driver module was built with a different ver
sion of DBI than the one currently being used. You
should rebuild the DBD module under the current ver
sion of DBI.
(Some rare platforms require "static linking". On
those platforms, there may be an old DBI or DBD driver
version actually embedded in the Perl executable being
used.)
DBD driver has not implemented the AutoCommit attribute
The DBD driver implementation is incomplete. Consult
the author.
Can't [sg]et %s->{%s}: unrecognised attribute
You attempted to set or get an unknown attribute of a
handle. Make sure you have spelled the attribute name
correctly; case is significant (e.g., "Autocommit" is
not the same as "AutoCommit").
Warnings
Database handle destroyed without explicit disconnect
A `$dbh' handle went out of scope or the program ended
before the handle was disconnected from the database.
You should always explicitly call `disconnect' when
you are finished using a database handle. If using
transactions then you should also explicitly call
`commit' or `rollback' before `disconnect'.
DBI Handle cleared whilst still holding %d cached kids!
Most probably due to a DBI bug. Possibly a DBD driver
bug. Please report it.
DBI Handle cleared whilst still active!
Most probably due to a DBI bug. Possibly a DBD driver
bug. Please report it.
Most probably a DBD driver bug. Please report it.
DBI Handle has %d uncleared child handles
Most probably due to a DBI bug. Possibly a DBD driver
bug. Please report it.
SEE ALSO
Driver and Database Documentation
Refer to the documentation for the DBD driver that you are
using.
Refer to the SQL Language Reference Manual for the
database engine that you are using.
Books and Journals
Programming the Perl DBI, by Alligator Descartes and Tim Bunce.
Programming Perl 2nd Ed. by Larry Wall, Tom Christiansen & Randal Schwartz.
Learning Perl by Randal Schwartz.
Dr Dobb's Journal, November 1996.
The Perl Journal, April 1997.
Manual Pages
perl(1), perlmod(1), perlbook(1)
Mailing List
The dbi-users mailing list is the primary means of commu
nication among users of the DBI and its related modules.
For details send email to:
dbi-users-help@perl.org
There are typically between 700 and 900 messages per
month. You have to subscribe in order to be able to post.
However you can opt for a 'post-only' subscription.
Mailing list archives are held at:
http://www.xray.mpe.mpg.de/mailing-lists/dbi/
http://groups.yahoo.com/group/dbi-users
http://www.bitmechanic.com/mail-archives/dbi-users/
http://marc.theaimsgroup.com/?l=perl-dbi&r=1&w=2
http://www.mail-archive.com/dbi-users%40perl.org/
http://www.mail-archive.com/dbi-users%40perl.org/
The DBI "Home Page":
http://dbi.perl.org/
Other DBI related links:
http://tegan.deltanet.com/~phlip/DBUIdoc.html
http://dc.pm.org/perl_db.html
http://wdvl.com/Authoring/DB/Intro/toc.html
http://www.hotwired.com/webmonkey/backend/tutorials/tutorial1.html
http://bumppo.net/lists/macperl/1999/06/msg00197.html
Other database related links:
http://www.jcc.com/sql_stnd.html
http://cuiwww.unige.ch/OSG/info/FreeDB/FreeDB.home.html
Commercial and Data Warehouse Links
http://www.dwinfocenter.org
http://www.datawarehouse.com
http://www.datamining.org
http://www.olapcouncil.org
http://www.idwa.org
http://www.knowledgecenters.org/dwcenter.asp
Recommended Perl Programming Links
http://language.perl.com/style/
FAQ
Please also read the DBI FAQ which is installed as a
DBI::FAQ module. You can use perldoc to read it by exe
cuting the `perldoc DBI::FAQ' command.
AUTHORS
DBI by Tim Bunce. This pod text by Tim Bunce, J. Douglas
Dunlop, Jonathan Leffler and others. Perl by Larry Wall
and the `perl5-porters'.
COPYRIGHT
The DBI module is Copyright (c) 1994-2000 Tim Bunce. Eng
land. All rights reserved.
You may distribute under the terms of either the GNU Gen
eral Public License or the Artistic License, as specified
in the Perl README file.
ACKNOWLEDGEMENTS
I would like to acknowledge the valuable contributions of
especially in the early years (1992-1994). In no particu
lar order: Kevin Stock, Buzz Moschetti, Kurt Andersen, Ted
Lemon, William Hails, Garth Kennedy, Michael Peppler, Neil
S. Briscoe, Jeff Urlwin, David J. Hughes, Jeff Stander,
Forrest D Whitcher, Larry Wall, Jeff Fried, Roy Johnson,
Paul Hudson, Georg Rehfeld, Steve Sizemore, Ron Pool, Jon
Meek, Tom Christiansen, Steve Baumgarten, Randal Schwartz,
and a whole lot more.
Then, of course, there are the poor souls who have strug
gled through untold and undocumented obstacles to actually
implement DBI drivers. Among their ranks are Jochen Wied
mann, Alligator Descartes, Jonathan Leffler, Jeff Urlwin,
Michael Peppler, Henrik Tougaard, Edwin Pratomo, Davide
Migliavacca, Jan Pazdziora, Peter Haworth, Edmund Mergl,
Steve Williams, Thomas Lowery, and Phlip Plumlee. Without
them, the DBI would not be the practical reality it is
today. I'm also especially grateful to Alligator
Descartes for starting work on the "Programming the Perl
DBI" book and letting me jump on board.
TRANSLATIONS
A German translation of this manual (possibly slightly out
of date) is available, thanks to O'Reilly, at:
http://www.oreilly.de/catalog/perldbiger/
Some other translations:
http://cronopio.net/perl/ - Spanish
http://member.nifty.ne.jp/hippo2000/dbimemo.htm - Japanese
SUPPORT / WARRANTY
The DBI is free software. IT COMES WITHOUT WARRANTY OF ANY
KIND.
Commercial support for Perl and the DBI, DBD::Oracle and
Oraperl modules can be arranged via The Perl Clinic. For
more details visit:
http://www.perlclinic.com
TRAINING
References to DBI related training resources. No recommen
dation implied.
http://www.treepax.co.uk/
http://www.keller.com/dbweb/
See the DBI FAQ for a more comprehensive list of FAQs. Use
the `perldoc DBI::FAQ' command to read it.
How fast is the DBI?
To measure the speed of the DBI and DBD::Oracle code, I
modified DBD::Oracle so you can set an attribute that will
cause the same row to be fetched from the row cache over
and over again (without involving Oracle code but exercis
ing *all* the DBI and DBD::Oracle code in the code path
for a fetch).
The results (on my lightly loaded old Sparc 10) fetching
50000 rows using:
1 while $csr->fetch;
were: one field: 5300 fetches per cpu second
(approx) ten fields: 4000 fetches per cpu second
(approx)
Obviously results will vary between platforms (newer
faster platforms can reach around 50000 fetches per sec
ond), but it does give a feel for the maximum performance:
fast. By way of comparison, using the code:
1 while @row = $csr->fetchrow_array;
(`fetchrow_array' is roughly the same as `ora_fetch')
gives:
one field: 3100 fetches per cpu second (approx)
ten fields: 1000 fetches per cpu second (approx)
Notice the slowdown and the more dramatic impact of extra
fields. (The fields were all one char long. The impact
would be even bigger for longer strings.)
Changing that slightly to represent actually doing some
thing in Perl with the fetched data:
while(@row = $csr->fetchrow_array) {
$hash{++$i} = [ @row ];
}
gives: ten fields: 500 fetches per cpu second (approx)
That simple addition has *halved* the performance.
I therefore conclude that DBI and DBD::Oracle overheads
are small compared with Perl language overheads (and prob
ably database overheads).
replacing your fetch loop with just:
1 while $csr->fetch;
and time that. If that helps then point the finger at your
own code. If that doesn't help much then point the finger
at the database, the platform, the network etc. But think
carefully before pointing it at the DBI or your driver.
(Having said all that, if anyone can show me how to make
the DBI or drivers even more efficient, I'm all ears.)
Why doesn't my CGI script work right?
Read the information in the references below. Please do
not post CGI related questions to the dbi-users mailing
list (or to me).
http://www.perl.com/cgi-bin/pace/pub/doc/FAQs/cgi/perl-cgi-faq.html
http://www3.pair.com/webthing/docs/cgi/faqs/cgifaq.shtml
http://www-genome.wi.mit.edu/WWW/faqs/www-security-faq.html
http://www.boutell.com/faq/
http://www.perl.com/perl/faq/
General problems and good ideas:
Use the CGI::ErrorWrap module.
Remember that many env vars won't be set for CGI scripts.
How can I maintain a WWW connection to a database?
For information on the Apache httpd server and the
`mod_perl' module see
http://perl.apache.org/
What about ODBC?
A DBD::ODBC module is available.
Does the DBI have a year 2000 problem?
No. The DBI has no knowledge or understanding of dates at
all.
Individual drivers (DBD::*) may have some date handling
code but are unlikely to have year 2000 related problems
within their code. However, your application code which
uses the DBI and DBD drivers may have year 2000 related
problems if it has not been designed and written well.
of the Perl FAQ:
http://www.perl.com/CPAN/doc/FAQs/FAQ/PerlFAQ.html
OTHER RELATED WORK AND PERL MODULES
Apache::DBI by E.Mergl@bawue.de
To be used with the Apache daemon together with an
embedded Perl interpreter like `mod_perl'. Establishes
a database connection which remains open for the life
time of the HTTP daemon. This way the CGI connect and
disconnect for every database access becomes superflu
ous.
JDBC Server by Stuart 'Zen' Bishop zen@bf.rmit.edu.au
The server is written in Perl. The client classes that
talk to it are of course in Java. Thus, a Java applet
or application will be able to comunicate via the JDBC
API with any database that has a DBI driver installed.
The URL used is in the form
`jdbc:dbi://host.domain.etc:999/Driver/DBName'. It
seems to be very similar to some commercial products,
such as jdbcKona.
Remote Proxy DBD support
As of DBI 1.02, a complete implementation of a
DBD::Proxy driver and the DBI::ProxyServer are part of
the DBI distribution.
SQL Parser
Hugo van der Sanden <hv@crypt.compulink.co.uk>
Stephen Zander <stephen.zander@mckesson.com>
Based on the O'Reilly lex/yacc book examples and
`byacc'.
See also the SQL::Statement module, a very simple SQL
parser and engine, base of the DBD::CSV driver.
Man(1) output converted with
man2html