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Green_GoodERP18_FSJ_Standard/PostgreSQL/doc/postgresql/html/sql-createview.html

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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!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 V1.79.1" /><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 12.4 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">

  3. CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] [ RECURSIVE ] VIEW <em class="replaceable"><code>name</code></em> [ ( <em class="replaceable"><code>column_name</code></em> [, ...] ) ]

  4.     [ WITH ( <em class="replaceable"><code>view_option_name</code></em> [= <em class="replaceable"><code>view_option_value</code></em>] [, ... ] ) ]

  5.     AS <em class="replaceable"><code>query</code></em>

  6.     [ WITH [ CASCADED | LOCAL ] CHECK OPTION ]

  7. </pre></div><div class="refsect1" id="id-1.9.3.97.5"><h2>Description</h2><p>

  8.    <code class="command">CREATE VIEW</code> defines a view of a query.  The view

  9.    is not physically materialized. Instead, the query is run every time

  10.    the view is referenced in a query.

  11.   </p><p>

  12.    <code class="command">CREATE OR REPLACE VIEW</code> is similar, but if a view

  13.    of the same name already exists, it is replaced.  The new query must

  14.    generate the same columns that were generated by the existing view query

  15.    (that is, the same column names in the same order and with the same data

  16.    types), but it may add additional columns to the end of the list.  The

  17.    calculations giving rise to the output columns may be completely different.

  18.   </p><p>

  19.    If a schema name is given (for example, <code class="literal">CREATE VIEW

  20.    myschema.myview ...</code>) then the view is created in the specified

  21.    schema.  Otherwise it is created in the current schema.  Temporary

  22.    views exist in a special schema, so a schema name cannot be given

  23.    when creating a temporary view. The name of the view must be

  24.    distinct from the name of any other view, table, sequence, index or foreign table

  25.    in the same schema.

  26.   </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>

  27.       If specified, the view is created as a temporary view.

  28.       Temporary views are automatically dropped at the end of the

  29.       current session.  Existing

  30.       permanent relations with the same name are not visible to the

  31.       current session while the temporary view exists, unless they are

  32.       referenced with schema-qualified names.

  33.      </p><p>

  34.       If any of the tables referenced by the view are temporary,

  35.       the view is created as a temporary view (whether

  36.       <code class="literal">TEMPORARY</code> is specified or not).

  37.      </p></dd><dt><span class="term"><code class="literal">RECURSIVE</code>

  38.       <a id="id-1.9.3.97.6.2.2.1.2" class="indexterm"></a>

  39.     </span></dt><dd><p>

  40.       Creates a recursive view.  The syntax

  41. </p><pre class="synopsis">

  42. 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>;

  43. </pre><p>

  44.       is equivalent to

  45. </p><pre class="synopsis">

  46. 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>;

  47. </pre><p>

  48.       A view column name list must be specified for a recursive view.

  49.      </p></dd><dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt><dd><p>

  50.       The name (optionally schema-qualified) of a view to be created.

  51.      </p></dd><dt><span class="term"><em class="replaceable"><code>column_name</code></em></span></dt><dd><p>

  52.       An optional list of names to be used for columns of the view.

  53.       If not given, the column names are deduced from the query.

  54.      </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>

  55.       This clause specifies optional parameters for a view; the following

  56.       parameters are supported:

  57. 

  58.       </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>

  59.           This parameter may be either <code class="literal">local</code> or

  60.           <code class="literal">cascaded</code>, and is equivalent to specifying

  61.           <code class="literal">WITH [ CASCADED | LOCAL ] CHECK OPTION</code> (see below).

  62.           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>.

  63.          </p></dd><dt><span class="term"><code class="literal">security_barrier</code> (<code class="type">boolean</code>)</span></dt><dd><p>

  64.           This should be used if the view is intended to provide row-level

  65.           security.  See <a class="xref" href="rules-privileges.html" title="40.5. Rules and Privileges">Section 40.5</a> for full details.

  66.          </p></dd></dl></div><p>

  67.      </p></dd><dt><span class="term"><em class="replaceable"><code>query</code></em></span></dt><dd><p>

  68.       A <a class="xref" href="sql-select.html" title="SELECT"><span class="refentrytitle">SELECT</span></a> or

  69.       <a class="xref" href="sql-values.html" title="VALUES"><span class="refentrytitle">VALUES</span></a> command

  70.       which will provide the columns and rows of the view.

  71.      </p></dd><dt><span class="term"><code class="literal">WITH [ CASCADED | LOCAL ] CHECK OPTION</code>

  72.       <a id="id-1.9.3.97.6.2.7.1.2" class="indexterm"></a>

  73.       <a id="id-1.9.3.97.6.2.7.1.3" class="indexterm"></a>

  74.     </span></dt><dd><p>

  75.       This option controls the behavior of automatically updatable views.  When

  76.       this option is specified, <code class="command">INSERT</code> and <code class="command">UPDATE</code>

  77.       commands on the view will be checked to ensure that new rows satisfy the

  78.       view-defining condition (that is, the new rows are checked to ensure that

  79.       they are visible through the view).  If they are not, the update will be

  80.       rejected.  If the <code class="literal">CHECK OPTION</code> is not specified,

  81.       <code class="command">INSERT</code> and <code class="command">UPDATE</code> commands on the view are

  82.       allowed to create rows that are not visible through the view.  The

  83.       following check options are supported:

  84. 

  85.       </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">LOCAL</code></span></dt><dd><p>

  86.           New rows are only checked against the conditions defined directly in

  87.           the view itself.  Any conditions defined on underlying base views are

  88.           not checked (unless they also specify the <code class="literal">CHECK OPTION</code>).

  89.          </p></dd><dt><span class="term"><code class="literal">CASCADED</code></span></dt><dd><p>

  90.           New rows are checked against the conditions of the view and all

  91.           underlying base views.  If the <code class="literal">CHECK OPTION</code> is specified,

  92.           and neither <code class="literal">LOCAL</code> nor <code class="literal">CASCADED</code> is specified,

  93.           then <code class="literal">CASCADED</code> is assumed.

  94.          </p></dd></dl></div><p>

  95.      </p><p>

  96.       The <code class="literal">CHECK OPTION</code> may not be used with <code class="literal">RECURSIVE</code>

  97.       views.

  98.      </p><p>

  99.       Note that the <code class="literal">CHECK OPTION</code> is only supported on views that

  100.       are automatically updatable, and do not have <code class="literal">INSTEAD OF</code>

  101.       triggers or <code class="literal">INSTEAD</code> rules.  If an automatically updatable

  102.       view is defined on top of a base view that has <code class="literal">INSTEAD OF</code>

  103.       triggers, then the <code class="literal">LOCAL CHECK OPTION</code> may be used to check

  104.       the conditions on the automatically updatable view, but the conditions

  105.       on the base view with <code class="literal">INSTEAD OF</code> triggers will not be

  106.       checked (a cascaded check option will not cascade down to a

  107.       trigger-updatable view, and any check options defined directly on a

  108.       trigger-updatable view will be ignored).  If the view or any of its base

  109.       relations has an <code class="literal">INSTEAD</code> rule that causes the

  110.       <code class="command">INSERT</code> or <code class="command">UPDATE</code> command to be rewritten, then

  111.       all check options will be ignored in the rewritten query, including any

  112.       checks from automatically updatable views defined on top of the relation

  113.       with the <code class="literal">INSTEAD</code> rule.

  114.      </p></dd></dl></div></div><div class="refsect1" id="id-1.9.3.97.7"><h2>Notes</h2><p>

  115.     Use the <a class="xref" href="sql-dropview.html" title="DROP VIEW"><span class="refentrytitle">DROP VIEW</span></a>

  116.     statement to drop views.

  117.    </p><p>

  118.     Be careful that the names and types of the view's columns will be

  119.     assigned the way you want.  For example:

  120. </p><pre class="programlisting">

  121. CREATE VIEW vista AS SELECT 'Hello World';

  122. </pre><p>

  123.     is bad form because the column name defaults to <code class="literal">?column?</code>;

  124.     also, the column data type defaults to <code class="type">text</code>, which might not

  125.     be what you wanted.  Better style for a string literal in a view's

  126.     result is something like:

  127. </p><pre class="programlisting">

  128. CREATE VIEW vista AS SELECT text 'Hello World' AS hello;

  129. </pre><p>

  130.    </p><p>

  131.     Access to tables referenced in the view is determined by permissions of

  132.     the view owner.  In some cases, this can be used to provide secure but

  133.     restricted access to the underlying tables.  However, not all views are

  134.     secure against tampering; see <a class="xref" href="rules-privileges.html" title="40.5. Rules and Privileges">Section 40.5</a> for

  135.     details.  Functions called in the view are treated the same as if they had

  136.     been called directly from the query using the view.  Therefore the user of

  137.     a view must have permissions to call all functions used by the view.

  138.    </p><p>

  139.     When <code class="command">CREATE OR REPLACE VIEW</code> is used on an

  140.     existing view, only the view's defining SELECT rule is changed.

  141.     Other view properties, including ownership, permissions, and non-SELECT

  142.     rules, remain unchanged.  You must own the view

  143.     to replace it (this includes being a member of the owning role).

  144.    </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>

  145.     Simple views are automatically updatable: the system will allow

  146.     <code class="command">INSERT</code>, <code class="command">UPDATE</code> and <code class="command">DELETE</code> statements

  147.     to be used on the view in the same way as on a regular table.  A view is

  148.     automatically updatable if it satisfies all of the following conditions:

  149. 

  150.     </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>

  151.        The view must have exactly one entry in its <code class="literal">FROM</code> list,

  152.        which must be a table or another updatable view.

  153.       </p></li><li class="listitem"><p>

  154.        The view definition must not contain <code class="literal">WITH</code>,

  155.        <code class="literal">DISTINCT</code>, <code class="literal">GROUP BY</code>, <code class="literal">HAVING</code>,

  156.        <code class="literal">LIMIT</code>, or <code class="literal">OFFSET</code> clauses at the top level.

  157.       </p></li><li class="listitem"><p>

  158.        The view definition must not contain set operations (<code class="literal">UNION</code>,

  159.        <code class="literal">INTERSECT</code> or <code class="literal">EXCEPT</code>) at the top level.

  160.       </p></li><li class="listitem"><p>

  161.        The view's select list must not contain any aggregates, window functions

  162.        or set-returning functions.

  163.       </p></li></ul></div><p>

  164.    </p><p>

  165.     An automatically updatable view may contain a mix of updatable and

  166.     non-updatable columns.  A column is updatable if it is a simple reference

  167.     to an updatable column of the underlying base relation; otherwise the

  168.     column is read-only, and an error will be raised if an <code class="command">INSERT</code>

  169.     or <code class="command">UPDATE</code> statement attempts to assign a value to it.

  170.    </p><p>

  171.     If the view is automatically updatable the system will convert any

  172.     <code class="command">INSERT</code>, <code class="command">UPDATE</code> or <code class="command">DELETE</code> statement

  173.     on the view into the corresponding statement on the underlying base

  174.     relation.  <code class="command">INSERT</code> statements that have an <code class="literal">ON

  175.     CONFLICT UPDATE</code> clause are fully supported.

  176.    </p><p>

  177.     If an automatically updatable view contains a <code class="literal">WHERE</code>

  178.     condition, the condition restricts which rows of the base relation are

  179.     available to be modified by <code class="command">UPDATE</code> and <code class="command">DELETE</code>

  180.     statements on the view.  However, an <code class="command">UPDATE</code> is allowed to

  181.     change a row so that it no longer satisfies the <code class="literal">WHERE</code>

  182.     condition, and thus is no longer visible through the view.  Similarly,

  183.     an <code class="command">INSERT</code> command can potentially insert base-relation rows

  184.     that do not satisfy the <code class="literal">WHERE</code> condition and thus are not

  185.     visible through the view (<code class="literal">ON CONFLICT UPDATE</code> may

  186.     similarly affect an existing row not visible through the view).

  187.     The <code class="literal">CHECK OPTION</code> may be used to prevent

  188.     <code class="command">INSERT</code> and <code class="command">UPDATE</code> commands from creating

  189.     such rows that are not visible through the view.

  190.    </p><p>

  191.     If an automatically updatable view is marked with the

  192.     <code class="literal">security_barrier</code> property then all the view's <code class="literal">WHERE</code>

  193.     conditions (and any conditions using operators which are marked as <code class="literal">LEAKPROOF</code>)

  194.     will always be evaluated before any conditions that a user of the view has

  195.     added.   See <a class="xref" href="rules-privileges.html" title="40.5. Rules and Privileges">Section 40.5</a> for full details.  Note that,

  196.     due to this, rows which are not ultimately returned (because they do not

  197.     pass the user's <code class="literal">WHERE</code> conditions) may still end up being locked.

  198.     <code class="command">EXPLAIN</code> can be used to see which conditions are

  199.     applied at the relation level (and therefore do not lock rows) and which are

  200.     not.

  201.    </p><p>

  202.     A more complex view that does not satisfy all these conditions is

  203.     read-only by default: the system will not allow an insert, update, or

  204.     delete on the view.  You can get the effect of an updatable view by

  205.     creating <code class="literal">INSTEAD OF</code> triggers on the view, which must

  206.     convert attempted inserts, etc. on the view into appropriate actions

  207.     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

  208.     (see <a class="xref" href="sql-createrule.html" title="CREATE RULE"><span class="refentrytitle">CREATE RULE</span></a>), but in practice triggers are

  209.     easier to understand and use correctly.

  210.    </p><p>

  211.     Note that the user performing the insert, update or delete on the view

  212.     must have the corresponding insert, update or delete privilege on the

  213.     view.  In addition the view's owner must have the relevant privileges on

  214.     the underlying base relations, but the user performing the update does

  215.     not need any permissions on the underlying base relations (see

  216.     <a class="xref" href="rules-privileges.html" title="40.5. Rules and Privileges">Section 40.5</a>).

  217.    </p></div></div><div class="refsect1" id="id-1.9.3.97.8"><h2>Examples</h2><p>

  218.    Create a view consisting of all comedy films:

  219. 

  220. </p><pre class="programlisting">

  221. CREATE VIEW comedies AS

  222.     SELECT *

  223.     FROM films

  224.     WHERE kind = 'Comedy';

  225. </pre><p>

  226.    This will create a view containing the columns that are in the

  227.    <code class="literal">film</code> table at the time of view creation.  Though

  228.    <code class="literal">*</code> was used to create the view, columns added later to

  229.    the table will not be part of the view.

  230.   </p><p>

  231.    Create a view with <code class="literal">LOCAL CHECK OPTION</code>:

  232. 

  233. </p><pre class="programlisting">

  234. CREATE VIEW universal_comedies AS

  235.     SELECT *

  236.     FROM comedies

  237.     WHERE classification = 'U'

  238.     WITH LOCAL CHECK OPTION;

  239. </pre><p>

  240.    This will create a view based on the <code class="literal">comedies</code> view, showing

  241.    only films with <code class="literal">kind = 'Comedy'</code> and

  242.    <code class="literal">classification = 'U'</code>. Any attempt to <code class="command">INSERT</code> or

  243.    <code class="command">UPDATE</code> a row in the view will be rejected if the new row

  244.    doesn't have <code class="literal">classification = 'U'</code>, but the film

  245.    <code class="literal">kind</code> will not be checked.

  246.   </p><p>

  247.    Create a view with <code class="literal">CASCADED CHECK OPTION</code>:

  248. 

  249. </p><pre class="programlisting">

  250. CREATE VIEW pg_comedies AS

  251.     SELECT *

  252.     FROM comedies

  253.     WHERE classification = 'PG'

  254.     WITH CASCADED CHECK OPTION;

  255. </pre><p>

  256.    This will create a view that checks both the <code class="literal">kind</code> and

  257.    <code class="literal">classification</code> of new rows.

  258.   </p><p>

  259.    Create a view with a mix of updatable and non-updatable columns:

  260. 

  261. </p><pre class="programlisting">

  262. CREATE VIEW comedies AS

  263.     SELECT f.*,

  264.            country_code_to_name(f.country_code) AS country,

  265.            (SELECT avg(r.rating)

  266.             FROM user_ratings r

  267.             WHERE r.film_id = f.id) AS avg_rating

  268.     FROM films f

  269.     WHERE f.kind = 'Comedy';

  270. </pre><p>

  271.    This view will support <code class="command">INSERT</code>, <code class="command">UPDATE</code> and

  272.    <code class="command">DELETE</code>.  All the columns from the <code class="literal">films</code> table will

  273.    be updatable, whereas the computed columns <code class="literal">country</code> and

  274.    <code class="literal">avg_rating</code> will be read-only.

  275.   </p><p>

  276.    Create a recursive view consisting of the numbers from 1 to 100:

  277. </p><pre class="programlisting">

  278. CREATE RECURSIVE VIEW public.nums_1_100 (n) AS

  279.     VALUES (1)

  280. UNION ALL

  281.     SELECT n+1 FROM nums_1_100 WHERE n &lt; 100;

  282. </pre><p>

  283.    Notice that although the recursive view's name is schema-qualified in this

  284.    <code class="command">CREATE</code>, its internal self-reference is not schema-qualified.

  285.    This is because the implicitly-created CTE's name cannot be

  286.    schema-qualified.

  287.   </p></div><div class="refsect1" id="id-1.9.3.97.9"><h2>Compatibility</h2><p>

  288.    <code class="command">CREATE OR REPLACE VIEW</code> is a

  289.    <span class="productname">PostgreSQL</span> language extension.

  290.    So is the concept of a temporary view.

  291.    The <code class="literal">WITH ( ... )</code> clause is an extension as well.

  292.   </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>
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