CREATE VIEW - Constructs a virtual table


SYNOPSIS

       CREATE VIEW view AS SELECT query

   INPUTS
       view   The name of a view to be created.

       query  An  SQL  query  which  will provide the columns and
              rows of the view.

              Refer to the SELECT statement for more  information
              about valid arguments.

   OUTPUTS
       CREATE The  message  returned  if the view is successfully
              created.

       ERROR: Relation 'view' already exists
              This error occurs if  the  view  specified  already
              exists in the database.

       NOTICE create: attribute named "column" has an unknown
              type
              The view will be created having a  column  with  an
              unknown type if you do not specify it. For example,
              the following command gives a warning:

              CREATE VIEW vista AS SELECT 'Hello World'

              whereas this command does not:

              CREATE VIEW vista AS SELECT text 'Hello World'


DESCRIPTION

       CREATE VIEW will define a view of a table.  This  view  is
       not physically materialized. Specifically, a query rewrite
       retrieve  rule  is  automatically  generated  to   support
       retrieve operations on views.

   NOTES
       Currently, views are read only.

       Use the DROP VIEW statement to drop views.

       Create a view consisting of all Comedy films:

       CREATE VIEW kinds AS
           SELECT *
           FROM films
           WHERE kind = 'Comedy';

       SELECT * FROM kinds;

        code  |           title           | did | date_prod  |  kind  | len
       -------+---------------------------+-----+------------+--------+-------
        UA502 | Bananas                   | 105 | 1971-07-13 | Comedy | 01:22
        C_701 | There's a Girl in my Soup | 107 | 1970-06-11 | Comedy | 01:36
       (2 rows)


COMPATIBILITY

   SQL92
       SQL92  specifies some additional capabilities for the CRE­
       ATE VIEW statement:

       CREATE VIEW view [ column [, ...] ]
           AS SELECT expression [ AS colname ] [, ...]
           FROM table [ WHERE condition ]
           [ WITH [ CASCADE | LOCAL ] CHECK OPTION ]

       The optional clauses for the full SQL92 command are:

       CHECK OPTION
              This option is to do  with  updatable  views.   All
              INSERTs  and UPDATEs on the view will be checked to
              ensure data satisfy the view-defining condition. If
              they do not, the update will be rejected.

       LOCAL  Check for integrity on this view.

       CASCADE
              Check  for integrity on this view and on any depen­
              dent view. CASCADE is assumed  if  neither  CASCADE
              nor LOCAL is specified.


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