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CREATE VIEW

Name

CREATE VIEW  --  define a new view

Synopsis

CREATE [ OR REPLACE ] VIEW view [ ( column name list ) ] AS SELECT query
  

Inputs

view

The name (optionally schema-qualified) of a view to be created.

column name list

An optional list of names to be used for columns of the view. If given, these names override the column names that would be deduced from the SQL query.

query

An SQL query (that is, a SELECT statement) which will provide the columns and rows of the view.

Refer to SELECT for more information about valid arguments.

Outputs

CREATE VIEW

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.

WARNING: Attribute '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 defines a view of a query. The view is not physically materialized. Instead, a query rewrite rule (an ON SELECT rule) is automatically generated to support SELECT operations on views.

CREATE OR REPLACE VIEW is similar, but if a view of the same name already exists, it is replaced. You can only replace a view with a new query that generates the identical set of columns (i.e., same column names and data types).

If a schema name is given (for example, CREATE VIEW myschema.myview ...) then the view is created in the specified schema. Otherwise it is created in the current schema (the one at the front of the search path; see CURRENT_SCHEMA()). The view name must be distinct from the name of any other view, table, sequence, or index in the same schema.

Notes

Currently, views are read only: the system will not allow an insert, update, or delete on a view. You can get the effect of an updatable view by creating rules that rewrite inserts, etc. on the view into appropriate actions on other tables. For more information see CREATE RULE.

Use the DROP VIEW statement to drop views.

Usage

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 CREATE 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 INSERT and UPDATE commands 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 dependent view. CASCADE is assumed if neither CASCADE nor LOCAL is specified.

CREATE OR REPLACE VIEW is a PostgreSQL language extension.

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