CREATE VIEW(7) PostgreSQL 15.7 Documentation CREATE VIEW(7)
NAME
CREATE_VIEW - define a new view
SYNOPSIS
CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] [ RECURSIVE ] VIEW name [ ( column_name [, ...] ) ]
[ WITH ( view_option_name [= view_option_value] [, ... ] ) ]
AS query
[ WITH [ CASCADED | LOCAL ] CHECK OPTION ]
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
relation (table, sequence, index, view, materialized view, 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).
RECURSIVE
Creates a recursive view. The syntax
CREATE RECURSIVE VIEW [ schema . ] view_name (column_names) AS SELECT ...;
is equivalent to
CREATE VIEW [ schema . ] view_name AS WITH RECURSIVE view_name (column_names) AS (SELECT ...) SELECT column_names FROM view_name;
A view column name list must be specified for a recursive view.
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; the following
parameters are supported:
check_option (enum)
This parameter may be either local or cascaded, and is
equivalent to specifying WITH [ CASCADED | LOCAL ] CHECK OPTION
(see below).
security_barrier (boolean)
This should be used if the view is intended to provide
row-level security. See Section 41.5 for full details.
security_invoker (boolean)
This option causes the underlying base relations to be checked
against the privileges of the user of the view rather than the
view owner. See the notes below for full details.
All of the above options can be changed on existing views using
ALTER VIEW.
query
A SELECT or VALUES command which will provide the columns and rows
of the view.
WITH [ CASCADED | LOCAL ] CHECK OPTION
This option controls the behavior of automatically updatable views.
When this option is specified, INSERT and UPDATE commands 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 OPTION is not specified,
INSERT and UPDATE commands on the view are allowed to create rows
that are not visible through the view. The following check options
are supported:
LOCAL
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 CHECK OPTION).
CASCADED
New rows are checked against the conditions of the view and all
underlying base views. If the CHECK OPTION is specified, and
neither LOCAL nor CASCADED is specified, then CASCADED is
assumed.
The CHECK OPTION may not be used with RECURSIVE views.
Note that the CHECK OPTION is only supported on views that are
automatically updatable, and do not have INSTEAD OF triggers or
INSTEAD rules. If an automatically updatable view is defined on top
of a base view that has INSTEAD OF triggers, then the LOCAL CHECK
OPTION may be used to check the conditions on the automatically
updatable view, but the conditions on the base view with INSTEAD OF
triggers 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 INSTEAD rule that
causes the INSERT or UPDATE command 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 INSTEAD rule.
NOTES
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 ?column?; also, the
column data type defaults to text, 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;
By default, access to the underlying base relations referenced in the
view is determined by the 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 41.5 for details.
If the view has the security_invoker property set to true, access to
the underlying base relations is determined by the permissions of the
user executing the query, rather than the view owner. Thus, the user of
a security invoker view must have the relevant permissions on the view
and its underlying base relations.
If any of the underlying base relations is a security invoker view, it
will be treated as if it had been accessed directly from the original
query. Thus, a security invoker view will always check its underlying
base relations using the permissions of the current user, even if it is
accessed from a view without the security_invoker property.
If any of the underlying base relations has row-level security enabled,
then by default, the row-level security policies of the view owner are
applied, and access to any additional relations referred to by those
policies is determined by the permissions of the view owner. However,
if the view has security_invoker set to true, then the policies and
permissions of the invoking user are used instead, as if the base
relations had been referenced directly from the query using the view.
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.
Functions in the view are executed with the privileges of the user
executing the query or the function owner, depending on whether the
functions are defined as SECURITY INVOKER or SECURITY DEFINER. Thus,
for example, calling CURRENT_USER directly in a view will always return
the invoking user, not the view owner. This is not affected by the
view's security_invoker setting, and so a view with security_invoker
set to false is not equivalent to a SECURITY DEFINER function and those
concepts should not be confused.
The user creating or replacing a view must have USAGE privileges on any
schemas referred to in the view query, in order to look up the
referenced objects in those schemas. Note, however, that this lookup
only happens when the view is created or replaced. Therefore, the user
of the view only requires the USAGE privilege on the schema containing
the view, not on the schemas referred to in the view query, even for a
security invoker view.
When CREATE OR REPLACE VIEW is used on an existing view, only the
view's defining SELECT rule, plus any WITH ( ... ) parameters and its
CHECK OPTION are 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).
Updatable Views
Simple views are automatically updatable: the system will allow INSERT,
UPDATE and DELETE statements 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 FROM list, which must
be a table or another updatable view.
• The view definition must not contain WITH, DISTINCT, GROUP BY,
HAVING, LIMIT, or OFFSET clauses at the top level.
• The view definition must not contain set operations (UNION,
INTERSECT or 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
INSERT or UPDATE statement attempts to assign a value to it.
If the view is automatically updatable the system will convert any
INSERT, UPDATE or DELETE statement on the view into the corresponding
statement on the underlying base relation. INSERT statements that have
an ON CONFLICT UPDATE clause are fully supported.
If an automatically updatable view contains a WHERE condition, the
condition restricts which rows of the base relation are available to be
modified by UPDATE and DELETE statements on the view. However, an
UPDATE is allowed to change a row so that it no longer satisfies the
WHERE condition, and thus is no longer visible through the view.
Similarly, an INSERT command can potentially insert base-relation rows
that do not satisfy the WHERE condition and thus are not visible
through the view (ON CONFLICT UPDATE may similarly affect an existing
row not visible through the view). The CHECK OPTION may be used to
prevent INSERT and UPDATE commands from creating such rows that are not
visible through the view.
If an automatically updatable view is marked with the security_barrier
property then all the view's WHERE conditions (and any conditions using
operators which are marked as LEAKPROOF) will always be evaluated
before any conditions that a user of the view has added. See
Section 41.5 for full details. Note that, due to this, rows which are
not ultimately returned (because they do not pass the user's WHERE
conditions) may still end up being locked. EXPLAIN can be used to see
which conditions are applied at the relation level (and therefore do
not lock rows) and which are not.
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
creating INSTEAD OF 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.
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, by default, the view's owner must have the relevant
privileges on the underlying base relations, whereas the user
performing the update does not need any permissions on the underlying
base relations (see Section 41.5). However, if the view has
security_invoker set to true, the user performing the update, rather
than the view owner, must have the relevant privileges on the
underlying base relations.
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.
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 comedies view, showing only films
with kind = 'Comedy' and classification = 'U'. Any attempt to INSERT or
UPDATE a row in the view will be rejected if the new row doesn't have
classification = 'U', but the film kind 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 kind and classification 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 INSERT, UPDATE and DELETE. All the columns from
the films table will be updatable, whereas the computed columns country
and avg_rating 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 CREATE, its internal self-reference is not schema-qualified. This
is because the implicitly-created CTE's name cannot be
schema-qualified.
COMPATIBILITY
CREATE OR REPLACE VIEW is a PostgreSQL language extension. So is the
concept of a temporary view. The WITH ( ... ) clause is an extension as
well, as are security barrier views and security invoker views.
SEE ALSO
ALTER VIEW (ALTER_VIEW(7)), DROP VIEW (DROP_VIEW(7)), CREATE
MATERIALIZED VIEW (CREATE_MATERIALIZED_VIEW(7))
PostgreSQL 15.7 2024 CREATE VIEW(7)
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