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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)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
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