NAME
CREATE VIEW - define a new view
SYNOPSIS
CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] VIEW name [ ( column_name [, ...] ) ]
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, or index 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.
query A SELECT [select(7)] or VALUES [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 rules that rewrite inserts, etc. on the view into
appropriate actions on other tables. For more information see CREATE
RULE [create_rule(7)].
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. However, 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’;
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)]