CREATE VIEW(7)		PostgreSQL 9.2.24 Documentation		CREATE VIEW(7)



NAME
       CREATE_VIEW - define a new view

SYNOPSIS
       CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] VIEW name [ ( column_name [, ...] ) ]
	   [ WITH ( view_option_name [= view_option_value] [, ... ] ) ]
	   AS query

DESCRIPTION
       CREATE VIEW defines a view of a query. The view is not physically
       materialized. Instead, the query is run every time the view is
       referenced in a query.

       CREATE OR REPLACE VIEW is similar, but if a view of the same name
       already exists, it is replaced. The new query must generate the same
       columns that were generated by the existing view query (that is, the
       same column names in the same order and with the same data types), but
       it may add additional columns to the end of the list. The calculations
       giving rise to the output columns may be completely different.

       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. Temporary views exist in a special
       schema, so a schema name cannot be given when creating a temporary
       view. The name of the view must be distinct from the name of any other
       view, table, sequence, index or foreign table in the same schema.

PARAMETERS
       TEMPORARY or TEMP
	   If specified, the view is created as a temporary view. Temporary
	   views are automatically dropped at the end of the current session.
	   Existing permanent relations with the same name are not visible to
	   the current session while the temporary view exists, unless they
	   are referenced with schema-qualified names.

	   If any of the tables referenced by the view are temporary, the view
	   is created as a temporary view (whether TEMPORARY is specified or
	   not).

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

       column_name
	   An optional list of names to be used for columns of the view. If
	   not given, the column names are deduced from the query.

       WITH ( view_option_name [= view_option_value] [, ... ] )
	   This clause specifies optional parameters for a view; currently,
	   the only supported parameter name is security_barrier, which should
	   be enabled when a view is intended to provide row-level security.
	   See Section 37.4, "Rules and Privileges", in the documentation for
	   full details.

       query
	   A SELECT(7) or VALUES(7) command which will provide the columns and
	   rows of the view.

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 INSTEAD triggers on the view, which must convert
       attempted inserts, etc. on the view into appropriate actions on other
       tables. For more information see CREATE TRIGGER (CREATE_TRIGGER(7)).
       Another possibility is to create rules (see CREATE RULE
       (CREATE_RULE(7))), but in practice triggers are easier to understand
       and use correctly.

       Use the DROP VIEW (DROP_VIEW(7)) statement to drop views.

       Be careful that the names and types of the view's columns will be
       assigned the way you want. For example:

	   CREATE VIEW vista AS SELECT 'Hello World';

       is bad form in two ways: the column name defaults to ?column?, and the
       column data type defaults to unknown. If you want a string literal in a
       view's result, use something like:

	   CREATE VIEW vista AS SELECT text 'Hello World' AS hello;

       Access to tables referenced in the view is determined by permissions of
       the view owner. In some cases, this can be used to provide secure but
       restricted access to the underlying tables. However, not all views are
       secure against tampering; see Section 37.4, "Rules and Privileges", in
       the documentation for details. Functions called in the view are treated
       the same as if they had been called directly from the query using the
       view. Therefore the user of a view must have permissions to call all
       functions used by the view.

       When CREATE OR REPLACE VIEW is used on an existing view, only the
       view's defining SELECT rule is changed. Other view properties,
       including ownership, permissions, and non-SELECT rules, remain
       unchanged. You must own the view to replace it (this includes being a
       member of the owning role).

EXAMPLES
       Create a view consisting of all comedy films:

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

       This will create a view containing the columns that are in the film
       table at the time of view creation. Though * was used to create the
       view, columns added later to the table will not be part of the view.

COMPATIBILITY
       The SQL standard specifies some additional capabilities for the CREATE
       VIEW statement:

	   CREATE VIEW name [ ( column_name [, ...] ) ]
	       AS query
	       [ WITH [ CASCADED | LOCAL ] CHECK OPTION ]

       The optional clauses for the full SQL command are:

       CHECK OPTION
	   This option has to do with updatable views. All INSERT and UPDATE
	   commands on the view will be checked to ensure data satisfy the
	   view-defining condition (that is, the new data would be visible
	   through the view). If they do not, the update will be rejected.

       LOCAL
	   Check for integrity on this view.

       CASCADED
	   Check for integrity on this view and on any dependent view.
	   CASCADED is assumed if neither CASCADED nor LOCAL is specified.

       CREATE OR REPLACE VIEW is a PostgreSQL language extension. So is the
       concept of a temporary view.

SEE ALSO
       ALTER VIEW (ALTER_VIEW(7)), DROP VIEW (DROP_VIEW(7))



PostgreSQL 9.2.24		  2017-11-06			CREATE VIEW(7)