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Green_GoodERP18_FSJ_Standard/PostgreSQL/doc/postgresql/html/sql-createcollation.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 COLLATION</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-createcast.html" title="CREATE CAST" /><link rel="next" href="sql-createconversion.html" title="CREATE CONVERSION" /></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 COLLATION</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-createcast.html" title="CREATE CAST">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-createconversion.html" title="CREATE CONVERSION">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-CREATECOLLATION"><div class="titlepage"></div><a id="id-1.9.3.59.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">CREATE COLLATION</span></h2><p>CREATE COLLATION — define a new collation</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">

  3. CREATE COLLATION [ IF NOT EXISTS ] <em class="replaceable"><code>name</code></em> (

  4.     [ LOCALE = <em class="replaceable"><code>locale</code></em>, ]

  5.     [ LC_COLLATE = <em class="replaceable"><code>lc_collate</code></em>, ]

  6.     [ LC_CTYPE = <em class="replaceable"><code>lc_ctype</code></em>, ]

  7.     [ PROVIDER = <em class="replaceable"><code>provider</code></em>, ]

  8.     [ DETERMINISTIC = <em class="replaceable"><code>boolean</code></em>, ]

  9.     [ VERSION = <em class="replaceable"><code>version</code></em> ]

  10. )

  11. CREATE COLLATION [ IF NOT EXISTS ] <em class="replaceable"><code>name</code></em> FROM <em class="replaceable"><code>existing_collation</code></em>

  12. </pre></div><div class="refsect1" id="SQL-CREATECOLLATION-DESCRIPTION"><h2>Description</h2><p>

  13.    <code class="command">CREATE COLLATION</code> defines a new collation using

  14.    the specified operating system locale settings,

  15.    or by copying an existing collation.

  16.  </p><p>

  17.    To be able to create a collation, you must

  18.    have <code class="literal">CREATE</code> privilege on the destination schema.

  19.   </p></div><div class="refsect1" id="id-1.9.3.59.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">IF NOT EXISTS</code></span></dt><dd><p>

  20.        Do not throw an error if a collation with the same name already exists.

  21.        A notice is issued in this case. Note that there is no guarantee that

  22.        the existing collation is anything like the one that would have been created.

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

  24.        The name of the collation. The collation name can be

  25.        schema-qualified. If it is not, the collation is defined in the

  26.        current schema. The collation name must be unique within that

  27.        schema.  (The system catalogs can contain collations with the

  28.        same name for other encodings, but these are ignored if the

  29.        database encoding does not match.)

  30.       </p></dd><dt><span class="term"><em class="replaceable"><code>locale</code></em></span></dt><dd><p>

  31.        This is a shortcut for setting <code class="symbol">LC_COLLATE</code>

  32.        and <code class="symbol">LC_CTYPE</code> at once.  If you specify this,

  33.        you cannot specify either of those parameters.

  34.       </p></dd><dt><span class="term"><em class="replaceable"><code>lc_collate</code></em></span></dt><dd><p>

  35.        Use the specified operating system locale for

  36.        the <code class="symbol">LC_COLLATE</code> locale category.

  37.       </p></dd><dt><span class="term"><em class="replaceable"><code>lc_ctype</code></em></span></dt><dd><p>

  38.        Use the specified operating system locale for

  39.        the <code class="symbol">LC_CTYPE</code> locale category.

  40.       </p></dd><dt><span class="term"><em class="replaceable"><code>provider</code></em></span></dt><dd><p>

  41.        Specifies the provider to use for locale services associated with this

  42.        collation.  Possible values

  43.        are: <code class="literal">icu</code>,<a id="id-1.9.3.59.6.2.6.2.1.2" class="indexterm"></a>

  44.        <code class="literal">libc</code>.

  45.        <code class="literal">libc</code> is the default.

  46.        The available choices depend on the operating system and build options.

  47.       </p></dd><dt><span class="term"><code class="literal">DETERMINISTIC</code></span></dt><dd><p>

  48.        Specifies whether the collation should use deterministic comparisons.

  49.        The default is true.  A deterministic comparison considers strings that

  50.        are not byte-wise equal to be unequal even if they are considered

  51.        logically equal by the comparison.  PostgreSQL breaks ties using a

  52.        byte-wise comparison.  Comparison that is not deterministic can make the

  53.        collation be, say, case- or accent-insensitive.  For that, you need to

  54.        choose an appropriate <code class="literal">LC_COLLATE</code> setting

  55.        <span class="emphasis"><em>and</em></span> set the collation to not deterministic here.

  56.       </p><p>

  57.        Nondeterministic collations are only supported with the ICU provider.

  58.       </p></dd><dt><span class="term"><em class="replaceable"><code>version</code></em></span></dt><dd><p>

  59.        Specifies the version string to store with the collation.  Normally,

  60.        this should be omitted, which will cause the version to be computed

  61.        from the actual version of the collation as provided by the operating

  62.        system.  This option is intended to be used

  63.        by <code class="command">pg_upgrade</code> for copying the version from an

  64.        existing installation.

  65.       </p><p>

  66.        See also <a class="xref" href="sql-altercollation.html" title="ALTER COLLATION"><span class="refentrytitle">ALTER COLLATION</span></a> for how to handle

  67.        collation version mismatches.

  68.       </p></dd><dt><span class="term"><em class="replaceable"><code>existing_collation</code></em></span></dt><dd><p>

  69.        The name of an existing collation to copy.  The new collation

  70.        will have the same properties as the existing one, but it

  71.        will be an independent object.

  72.       </p></dd></dl></div></div><div class="refsect1" id="SQL-CREATECOLLATION-NOTES"><h2>Notes</h2><p>

  73.    <code class="command">CREATE COLLATION</code> takes a <code class="literal">SHARE ROW

  74.    EXCLUSIVE</code> lock, which is self-conflicting, on the

  75.    <code class="structname">pg_collation</code> system catalog, so only one

  76.    <code class="command">CREATE COLLATION</code> command can run at a time.

  77.   </p><p>

  78.    Use <code class="command">DROP COLLATION</code> to remove user-defined collations.

  79.   </p><p>

  80.    See <a class="xref" href="collation.html#COLLATION-CREATE" title="23.2.2.3. Creating New Collation Objects">Section 23.2.2.3</a> for more information on how to create collations.

  81.   </p><p>

  82.    When using the <code class="literal">libc</code> collation provider, the locale must

  83.    be applicable to the current database encoding.

  84.    See <a class="xref" href="sql-createdatabase.html" title="CREATE DATABASE"><span class="refentrytitle">CREATE DATABASE</span></a> for the precise rules.

  85.   </p></div><div class="refsect1" id="SQL-CREATECOLLATION-EXAMPLES"><h2>Examples</h2><p>

  86.    To create a collation from the operating system locale

  87.    <code class="literal">fr_FR.utf8</code>

  88.    (assuming the current database encoding is <code class="literal">UTF8</code>):

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

  90. CREATE COLLATION french (locale = 'fr_FR.utf8');

  91. </pre><p>

  92.   </p><p>

  93.    To create a collation using the ICU provider using German phone book sort order:

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

  95. CREATE COLLATION german_phonebook (provider = icu, locale = 'de-u-co-phonebk');

  96. </pre><p>

  97.   </p><p>

  98.    To create a collation from an existing collation:

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

  100. CREATE COLLATION german FROM "de_DE";

  101. </pre><p>

  102.    This can be convenient to be able to use operating-system-independent

  103.    collation names in applications.

  104.   </p></div><div class="refsect1" id="SQL-CREATECOLLATION-COMPAT"><h2>Compatibility</h2><p>

  105.    There is a <code class="command">CREATE COLLATION</code> statement in the SQL

  106.    standard, but it is limited to copying an existing collation.  The

  107.    syntax to create a new collation is

  108.    a <span class="productname">PostgreSQL</span> extension.

  109.   </p></div><div class="refsect1" id="SQL-CREATECOLLATION-SEEALSO"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-altercollation.html" title="ALTER COLLATION"><span class="refentrytitle">ALTER COLLATION</span></a>, <a class="xref" href="sql-dropcollation.html" title="DROP COLLATION"><span class="refentrytitle">DROP COLLATION</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-createcast.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-createconversion.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">CREATE CAST </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> CREATE CONVERSION</td></tr></table></div></body></html>
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