trusty (7) CREATE_VIEW.7.gz

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

           Note
           The following description applies both to Postgres-XC and PostgreSQL if not described explicitly.

       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
           TEMPORARY views have not been supported by Postgres-XC. This may be supported by the future releases.

       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 38.4, “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 38.4, “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))