CREATE VIEW - define a new view
CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] [ RECURSIVE ] VIEW
column_name[, ...] ) ] [ WITH (
view_option_value] [, ... ] ) ] AS
query[ WITH [ CASCADED | LOCAL ] CHECK OPTION ]
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,
) 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.
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
TEMPORARYis specified or not).
Creates a recursive view. The syntax
CREATE RECURSIVE VIEW [
column_names) AS SELECT
is equivalent to
CREATE VIEW [
view_nameAS WITH RECURSIVE
column_names) AS (SELECT
A view column name list must be specified for a recursive view.
The name (optionally schema-qualified) of a view to be created.
An optional list of names to be used for columns of the view. If not given, the column names are deduced from the query.
view_option_value] [, ... ] )
This clause specifies optional parameters for a view; the following parameters are supported:
This parameter may be either
cascaded, and is equivalent to specifying
WITH [ CASCADED | LOCAL ] CHECK OPTION(see below). This option can be changed on existing views using ALTER VIEW .
This should be used if the view is intended to provide row-level security. See Section 40.5 for full details.
WITH [ CASCADED | LOCAL ] CHECK OPTION
This option controls the behavior of automatically updatable views. When this option is specified,
UPDATEcommands on the view will be checked to ensure that new rows satisfy the view-defining condition (that is, the new rows are checked to ensure that they are visible through the view). If they are not, the update will be rejected. If the
CHECK OPTIONis not specified,
UPDATEcommands on the view are allowed to create rows that are not visible through the view. The following check options are supported:
New rows are only checked against the conditions defined directly in the view itself. Any conditions defined on underlying base views are not checked (unless they also specify the
New rows are checked against the conditions of the view and all underlying base views. If the
CHECK OPTIONis specified, and neither
CASCADEDis specified, then
CHECK OPTIONmay not be used with
Note that the
CHECK OPTIONis only supported on views that are automatically updatable, and do not have
INSTEAD OFtriggers or
INSTEADrules. If an automatically updatable view is defined on top of a base view that has
INSTEAD OFtriggers, then the
LOCAL CHECK OPTIONmay be used to check the conditions on the automatically updatable view, but the conditions on the base view with
INSTEAD OFtriggers will not be checked (a cascaded check option will not cascade down to a trigger-updatable view, and any check options defined directly on a trigger-updatable view will be ignored). If the view or any of its base relations has an
INSTEADrule that causes the
UPDATEcommand to be rewritten, then all check options will be ignored in the rewritten query, including any checks from automatically updatable views defined on top of the relation with the
Use the DROP VIEW 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 because the column name defaults to
also, the column data type defaults to
, which might not
be what you wanted. Better style for a string literal in a view's
result is 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 40.5 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.
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).
Simple views are automatically updatable: the system will allow
to be used on the view in the same way as on a regular table. A view is
automatically updatable if it satisfies all of the following conditions:
The view must have exactly one entry in its
FROMlist, which must be a table or another updatable view.
The view definition must not contain
OFFSETclauses at the top level.
The view definition must not contain set operations (
EXCEPT) at the top level.
The view's select list must not contain any aggregates, window functions or set-returning functions.
An automatically updatable view may contain a mix of updatable and
non-updatable columns. A column is updatable if it is a simple reference
to an updatable column of the underlying base relation; otherwise the
column is read-only, and an error will be raised if an
statement attempts to assign a value to it.
If the view is automatically updatable the system will convert any
on the view into the corresponding statement on the underlying base
statements that have an
clause are fully supported.
If an automatically updatable view contains a
condition, the condition restricts which rows of the base relation are
available to be modified by
statements on the view. However, an
is allowed to
change a row so that it no longer satisfies the
condition, and thus is no longer visible through the view. Similarly,
command can potentially insert base-relation rows
that do not satisfy the
condition and thus are not
visible through the view (
ON CONFLICT UPDATE
similarly affect an existing row not visible through the view).
may be used to prevent
commands from creating
such rows that are not visible through the view.
If an automatically updatable view is marked with the
property then all the view's
conditions (and any conditions using operators which are marked as
will always be evaluated before any conditions that a user of the view has
for full details. Note that,
due to this, rows which are not ultimately returned (because they do not
pass the user's
conditions) may still end up being locked.
can be used to see which conditions are
applied at the relation level (and therefore do not lock rows) and which are
A more complex view that does not satisfy all these conditions is
read-only by default: the system will not allow an insert, update, or
delete on the view. You can get the effect of an updatable view by
triggers on the view, which must
convert attempted inserts, etc. on the view into appropriate actions
on other tables. For more information see
. Another possibility is to create rules
), but in practice triggers are
easier to understand and use correctly.
Note that the user performing the insert, update or delete on the view must have the corresponding insert, update or delete privilege on the view. In addition the view's owner must have the relevant privileges on the underlying base relations, but the user performing the update does not need any permissions on the underlying base relations (see Section 40.5 ).
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
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.
Create a view with
LOCAL CHECK OPTION
CREATE VIEW universal_comedies AS SELECT * FROM comedies WHERE classification = 'U' WITH LOCAL CHECK OPTION;
This will create a view based on the
only films with
kind = 'Comedy'
classification = 'U'
. Any attempt to
a row in the view will be rejected if the new row
classification = 'U'
, but the film
will not be checked.
Create a view with
CASCADED CHECK OPTION
CREATE VIEW pg_comedies AS SELECT * FROM comedies WHERE classification = 'PG' WITH CASCADED CHECK OPTION;
This will create a view that checks both the
of new rows.
Create a view with a mix of updatable and non-updatable columns:
CREATE VIEW comedies AS SELECT f.*, country_code_to_name(f.country_code) AS country, (SELECT avg(r.rating) FROM user_ratings r WHERE r.film_id = f.id) AS avg_rating FROM films f WHERE f.kind = 'Comedy';
This view will support
. All the columns from the
be updatable, whereas the computed columns
will be read-only.
Create a recursive view consisting of the numbers from 1 to 100:
CREATE RECURSIVE VIEW public.nums_1_100 (n) AS VALUES (1) UNION ALL SELECT n+1 FROM nums_1_100 WHERE n < 100;
Notice that although the recursive view's name is schema-qualified in this
, its internal self-reference is not schema-qualified.
This is because the implicitly-created CTE's name cannot be
CREATE OR REPLACE VIEW
So is the concept of a temporary view.
WITH ( ... )
clause is an extension as well.