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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>CREATE VIEW</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="sql-createusermapping.html" title="CREATE USER MAPPING" /><link rel="next" href="sql-deallocate.html" title="DEALLOCATE" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">CREATE VIEW</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-createusermapping.html" title="CREATE USER MAPPING">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-deallocate.html" title="DEALLOCATE">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-CREATEVIEW"><div class="titlepage"></div><a id="id-1.9.3.97.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">CREATE VIEW</span></h2><p>CREATE VIEW — define a new view</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">
CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] [ RECURSIVE ] VIEW <em class="replaceable"><code>name</code></em> [ ( <em class="replaceable"><code>column_name</code></em> [, ...] ) ]
[ WITH ( <em class="replaceable"><code>view_option_name</code></em> [= <em class="replaceable"><code>view_option_value</code></em>] [, ... ] ) ]
AS <em class="replaceable"><code>query</code></em>
[ WITH [ CASCADED | LOCAL ] CHECK OPTION ]
</pre></div><div class="refsect1" id="id-1.9.3.97.5"><h2>Description</h2><p>
<code class="command">CREATE VIEW</code> 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.
</p><p>
<code class="command">CREATE OR REPLACE VIEW</code> 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.
</p><p>
If a schema name is given (for example, <code class="literal">CREATE VIEW
myschema.myview ...</code>) 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.
</p></div><div class="refsect1" id="id-1.9.3.97.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">TEMPORARY</code> or <code class="literal">TEMP</code></span></dt><dd><p>
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.
</p><p>
If any of the tables referenced by the view are temporary,
the view is created as a temporary view (whether
<code class="literal">TEMPORARY</code> is specified or not).
</p></dd><dt><span class="term"><code class="literal">RECURSIVE</code>
<a id="id-1.9.3.97.6.2.2.1.2" class="indexterm"></a>
</span></dt><dd><p>
Creates a recursive view. The syntax
</p><pre class="synopsis">
CREATE RECURSIVE VIEW [ <em class="replaceable"><code>schema</code></em> . ] <em class="replaceable"><code>view_name</code></em> (<em class="replaceable"><code>column_names</code></em>) AS SELECT <em class="replaceable"><code>...</code></em>;
</pre><p>
is equivalent to
</p><pre class="synopsis">
CREATE VIEW [ <em class="replaceable"><code>schema</code></em> . ] <em class="replaceable"><code>view_name</code></em> AS WITH RECURSIVE <em class="replaceable"><code>view_name</code></em> (<em class="replaceable"><code>column_names</code></em>) AS (SELECT <em class="replaceable"><code>...</code></em>) SELECT <em class="replaceable"><code>column_names</code></em> FROM <em class="replaceable"><code>view_name</code></em>;
</pre><p>
A view column name list must be specified for a recursive view.
</p></dd><dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt><dd><p>
The name (optionally schema-qualified) of a view to be created.
</p></dd><dt><span class="term"><em class="replaceable"><code>column_name</code></em></span></dt><dd><p>
An optional list of names to be used for columns of the view.
If not given, the column names are deduced from the query.
</p></dd><dt><span class="term"><code class="literal">WITH ( <em class="replaceable"><code>view_option_name</code></em> [= <em class="replaceable"><code>view_option_value</code></em>] [, ... ] )</code></span></dt><dd><p>
This clause specifies optional parameters for a view; the following
parameters are supported:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">check_option</code> (<code class="type">string</code>)</span></dt><dd><p>
This parameter may be either <code class="literal">local</code> or
<code class="literal">cascaded</code>, and is equivalent to specifying
<code class="literal">WITH [ CASCADED | LOCAL ] CHECK OPTION</code> (see below).
This option can be changed on existing views using <a class="xref" href="sql-alterview.html" title="ALTER VIEW"><span class="refentrytitle">ALTER VIEW</span></a>.
</p></dd><dt><span class="term"><code class="literal">security_barrier</code> (<code class="type">boolean</code>)</span></dt><dd><p>
This should be used if the view is intended to provide row-level
security. See <a class="xref" href="rules-privileges.html" title="41.5. Rules and Privileges">Section 41.5</a> for full details.
</p></dd></dl></div><p>
</p></dd><dt><span class="term"><em class="replaceable"><code>query</code></em></span></dt><dd><p>
A <a class="xref" href="sql-select.html" title="SELECT"><span class="refentrytitle">SELECT</span></a> or
<a class="xref" href="sql-values.html" title="VALUES"><span class="refentrytitle">VALUES</span></a> command
which will provide the columns and rows of the view.
</p></dd><dt><span class="term"><code class="literal">WITH [ CASCADED | LOCAL ] CHECK OPTION</code>
<a id="id-1.9.3.97.6.2.7.1.2" class="indexterm"></a>
<a id="id-1.9.3.97.6.2.7.1.3" class="indexterm"></a>
</span></dt><dd><p>
This option controls the behavior of automatically updatable views. When
this option is specified, <code class="command">INSERT</code> and <code class="command">UPDATE</code>
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 <code class="literal">CHECK OPTION</code> is not specified,
<code class="command">INSERT</code> and <code class="command">UPDATE</code> commands on the view are
allowed to create rows that are not visible through the view. The
following check options are supported:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">LOCAL</code></span></dt><dd><p>
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 <code class="literal">CHECK OPTION</code>).
</p></dd><dt><span class="term"><code class="literal">CASCADED</code></span></dt><dd><p>
New rows are checked against the conditions of the view and all
underlying base views. If the <code class="literal">CHECK OPTION</code> is specified,
and neither <code class="literal">LOCAL</code> nor <code class="literal">CASCADED</code> is specified,
then <code class="literal">CASCADED</code> is assumed.
</p></dd></dl></div><p>
</p><p>
The <code class="literal">CHECK OPTION</code> may not be used with <code class="literal">RECURSIVE</code>
views.
</p><p>
Note that the <code class="literal">CHECK OPTION</code> is only supported on views that
are automatically updatable, and do not have <code class="literal">INSTEAD OF</code>
triggers or <code class="literal">INSTEAD</code> rules. If an automatically updatable
view is defined on top of a base view that has <code class="literal">INSTEAD OF</code>
triggers, then the <code class="literal">LOCAL CHECK OPTION</code> may be used to check
the conditions on the automatically updatable view, but the conditions
on the base view with <code class="literal">INSTEAD OF</code> 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 <code class="literal">INSTEAD</code> rule that causes the
<code class="command">INSERT</code> or <code class="command">UPDATE</code> 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 <code class="literal">INSTEAD</code> rule.
</p></dd></dl></div></div><div class="refsect1" id="id-1.9.3.97.7"><h2>Notes</h2><p>
Use the <a class="xref" href="sql-dropview.html" title="DROP VIEW"><span class="refentrytitle">DROP VIEW</span></a>
statement to drop views.
</p><p>
Be careful that the names and types of the view's columns will be
assigned the way you want. For example:
</p><pre class="programlisting">
CREATE VIEW vista AS SELECT 'Hello World';
</pre><p>
is bad form because the column name defaults to <code class="literal">?column?</code>;
also, the column data type defaults to <code class="type">text</code>, which might not
be what you wanted. Better style for a string literal in a view's
result is something like:
</p><pre class="programlisting">
CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
</pre><p>
</p><p>
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 <a class="xref" href="rules-privileges.html" title="41.5. Rules and Privileges">Section 41.5</a> 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.
</p><p>
When <code class="command">CREATE OR REPLACE VIEW</code> 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).
</p><div class="refsect2" id="SQL-CREATEVIEW-UPDATABLE-VIEWS"><h3>Updatable Views</h3><a id="id-1.9.3.97.7.6.2" class="indexterm"></a><p>
Simple views are automatically updatable: the system will allow
<code class="command">INSERT</code>, <code class="command">UPDATE</code> and <code class="command">DELETE</code> 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:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
The view must have exactly one entry in its <code class="literal">FROM</code> list,
which must be a table or another updatable view.
</p></li><li class="listitem"><p>
The view definition must not contain <code class="literal">WITH</code>,
<code class="literal">DISTINCT</code>, <code class="literal">GROUP BY</code>, <code class="literal">HAVING</code>,
<code class="literal">LIMIT</code>, or <code class="literal">OFFSET</code> clauses at the top level.
</p></li><li class="listitem"><p>
The view definition must not contain set operations (<code class="literal">UNION</code>,
<code class="literal">INTERSECT</code> or <code class="literal">EXCEPT</code>) at the top level.
</p></li><li class="listitem"><p>
The view's select list must not contain any aggregates, window functions
or set-returning functions.
</p></li></ul></div><p>
</p><p>
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 <code class="command">INSERT</code>
or <code class="command">UPDATE</code> statement attempts to assign a value to it.
</p><p>
If the view is automatically updatable the system will convert any
<code class="command">INSERT</code>, <code class="command">UPDATE</code> or <code class="command">DELETE</code> statement
on the view into the corresponding statement on the underlying base
relation. <code class="command">INSERT</code> statements that have an <code class="literal">ON
CONFLICT UPDATE</code> clause are fully supported.
</p><p>
If an automatically updatable view contains a <code class="literal">WHERE</code>
condition, the condition restricts which rows of the base relation are
available to be modified by <code class="command">UPDATE</code> and <code class="command">DELETE</code>
statements on the view. However, an <code class="command">UPDATE</code> is allowed to
change a row so that it no longer satisfies the <code class="literal">WHERE</code>
condition, and thus is no longer visible through the view. Similarly,
an <code class="command">INSERT</code> command can potentially insert base-relation rows
that do not satisfy the <code class="literal">WHERE</code> condition and thus are not
visible through the view (<code class="literal">ON CONFLICT UPDATE</code> may
similarly affect an existing row not visible through the view).
The <code class="literal">CHECK OPTION</code> may be used to prevent
<code class="command">INSERT</code> and <code class="command">UPDATE</code> commands from creating
such rows that are not visible through the view.
</p><p>
If an automatically updatable view is marked with the
<code class="literal">security_barrier</code> property then all the view's <code class="literal">WHERE</code>
conditions (and any conditions using operators which are marked as <code class="literal">LEAKPROOF</code>)
will always be evaluated before any conditions that a user of the view has
added. See <a class="xref" href="rules-privileges.html" title="41.5. Rules and Privileges">Section 41.5</a> for full details. Note that,
due to this, rows which are not ultimately returned (because they do not
pass the user's <code class="literal">WHERE</code> conditions) may still end up being locked.
<code class="command">EXPLAIN</code> can be used to see which conditions are
applied at the relation level (and therefore do not lock rows) and which are
not.
</p><p>
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 <code class="literal">INSTEAD OF</code> triggers on the view, which must
convert attempted inserts, etc. on the view into appropriate actions
on other tables. For more information see <a class="xref" href="sql-createtrigger.html" title="CREATE TRIGGER"><span class="refentrytitle">CREATE TRIGGER</span></a>. Another possibility is to create rules
(see <a class="xref" href="sql-createrule.html" title="CREATE RULE"><span class="refentrytitle">CREATE RULE</span></a>), but in practice triggers are
easier to understand and use correctly.
</p><p>
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
<a class="xref" href="rules-privileges.html" title="41.5. Rules and Privileges">Section 41.5</a>).
</p></div></div><div class="refsect1" id="id-1.9.3.97.8"><h2>Examples</h2><p>
Create a view consisting of all comedy films:
</p><pre class="programlisting">
CREATE VIEW comedies AS
SELECT *
FROM films
WHERE kind = 'Comedy';
</pre><p>
This will create a view containing the columns that are in the
<code class="literal">film</code> table at the time of view creation. Though
<code class="literal">*</code> was used to create the view, columns added later to
the table will not be part of the view.
</p><p>
Create a view with <code class="literal">LOCAL CHECK OPTION</code>:
</p><pre class="programlisting">
CREATE VIEW universal_comedies AS
SELECT *
FROM comedies
WHERE classification = 'U'
WITH LOCAL CHECK OPTION;
</pre><p>
This will create a view based on the <code class="literal">comedies</code> view, showing
only films with <code class="literal">kind = 'Comedy'</code> and
<code class="literal">classification = 'U'</code>. Any attempt to <code class="command">INSERT</code> or
<code class="command">UPDATE</code> a row in the view will be rejected if the new row
doesn't have <code class="literal">classification = 'U'</code>, but the film
<code class="literal">kind</code> will not be checked.
</p><p>
Create a view with <code class="literal">CASCADED CHECK OPTION</code>:
</p><pre class="programlisting">
CREATE VIEW pg_comedies AS
SELECT *
FROM comedies
WHERE classification = 'PG'
WITH CASCADED CHECK OPTION;
</pre><p>
This will create a view that checks both the <code class="literal">kind</code> and
<code class="literal">classification</code> of new rows.
</p><p>
Create a view with a mix of updatable and non-updatable columns:
</p><pre class="programlisting">
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';
</pre><p>
This view will support <code class="command">INSERT</code>, <code class="command">UPDATE</code> and
<code class="command">DELETE</code>. All the columns from the <code class="literal">films</code> table will
be updatable, whereas the computed columns <code class="literal">country</code> and
<code class="literal">avg_rating</code> will be read-only.
</p><p>
Create a recursive view consisting of the numbers from 1 to 100:
</p><pre class="programlisting">
CREATE RECURSIVE VIEW public.nums_1_100 (n) AS
VALUES (1)
UNION ALL
SELECT n+1 FROM nums_1_100 WHERE n < 100;
</pre><p>
Notice that although the recursive view's name is schema-qualified in this
<code class="command">CREATE</code>, its internal self-reference is not schema-qualified.
This is because the implicitly-created CTE's name cannot be
schema-qualified.
</p></div><div class="refsect1" id="id-1.9.3.97.9"><h2>Compatibility</h2><p>
<code class="command">CREATE OR REPLACE VIEW</code> is a
<span class="productname">PostgreSQL</span> language extension.
So is the concept of a temporary view.
The <code class="literal">WITH ( ... )</code> clause is an extension as well.
</p></div><div class="refsect1" id="id-1.9.3.97.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-alterview.html" title="ALTER VIEW"><span class="refentrytitle">ALTER VIEW</span></a>, <a class="xref" href="sql-dropview.html" title="DROP VIEW"><span class="refentrytitle">DROP VIEW</span></a>, <a class="xref" href="sql-creatematerializedview.html" title="CREATE MATERIALIZED VIEW"><span class="refentrytitle">CREATE MATERIALIZED VIEW</span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-createusermapping.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-deallocate.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">CREATE USER MAPPING </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> DEALLOCATE</td></tr></table></div></body></html>
