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Green_GoodERP18_FSJ_Standard/PostgreSQL/doc/postgresql/html/infoschema-character-sets.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>36.7. character_sets</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="infoschema-attributes.html" title="36.6. attributes" /><link rel="next" href="infoschema-check-constraint-routine-usage.html" title="36.8. check_constraint_routine_usage" /></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">36.7. <code xmlns="http://www.w3.org/1999/xhtml" class="literal">character_sets</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="infoschema-attributes.html" title="36.6. attributes">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="information-schema.html" title="Chapter 36. The Information Schema">Up</a></td><th width="60%" align="center">Chapter 36. The Information Schema</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="infoschema-check-constraint-routine-usage.html" title="36.8. check_constraint_routine_usage">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="INFOSCHEMA-CHARACTER-SETS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">36.7. <code class="literal">character_sets</code></h2></div></div></div><p>

  3.    The view <code class="literal">character_sets</code> identifies the character

  4.    sets available in the current database.  Since PostgreSQL does not

  5.    support multiple character sets within one database, this view only

  6.    shows one, which is the database encoding.

  7.   </p><p>

  8.    Take note of how the following terms are used in the SQL standard:

  9.    </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">character repertoire</span></dt><dd><p>

  10.        An abstract collection of characters, for

  11.        example <code class="literal">UNICODE</code>, <code class="literal">UCS</code>, or

  12.        <code class="literal">LATIN1</code>.  Not exposed as an SQL object, but

  13.        visible in this view.

  14.       </p></dd><dt><span class="term">character encoding form</span></dt><dd><p>

  15.        An encoding of some character repertoire.  Most older character

  16.        repertoires only use one encoding form, and so there are no

  17.        separate names for them (e.g., <code class="literal">LATIN1</code> is an

  18.        encoding form applicable to the <code class="literal">LATIN1</code>

  19.        repertoire).  But for example Unicode has the encoding forms

  20.        <code class="literal">UTF8</code>, <code class="literal">UTF16</code>, etc. (not

  21.        all supported by PostgreSQL).  Encoding forms are not exposed

  22.        as an SQL object, but are visible in this view.

  23.       </p></dd><dt><span class="term">character set</span></dt><dd><p>

  24.        A named SQL object that identifies a character repertoire, a

  25.        character encoding, and a default collation.  A predefined

  26.        character set would typically have the same name as an encoding

  27.        form, but users could define other names.  For example, the

  28.        character set <code class="literal">UTF8</code> would typically identify

  29.        the character repertoire <code class="literal">UCS</code>, encoding

  30.        form <code class="literal">UTF8</code>, and some default collation.

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

  32. 

  33.    You can think of an <span class="quote">“<span class="quote">encoding</span>”</span> in PostgreSQL either as

  34.    a character set or a character encoding form.  They will have the

  35.    same name, and there can only be one in one database.

  36.   </p><div class="table" id="id-1.7.6.11.4"><p class="title"><strong>Table 36.5. <code class="literal">character_sets</code> Columns</strong></p><div class="table-contents"><table class="table" summary="character_sets Columns" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Name</th><th>Data Type</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">character_set_catalog</code></td><td><code class="literal">sql_identifier</code></td><td>Character sets are currently not implemented as schema objects, so this column is null.</td></tr><tr><td><code class="literal">character_set_schema</code></td><td><code class="literal">sql_identifier</code></td><td>Character sets are currently not implemented as schema objects, so this column is null.</td></tr><tr><td><code class="literal">character_set_name</code></td><td><code class="literal">sql_identifier</code></td><td>Name of the character set, currently implemented as showing the name of the database encoding</td></tr><tr><td><code class="literal">character_repertoire</code></td><td><code class="literal">sql_identifier</code></td><td>Character repertoire, showing <code class="literal">UCS</code> if the encoding is <code class="literal">UTF8</code>, else just the encoding name</td></tr><tr><td><code class="literal">form_of_use</code></td><td><code class="literal">sql_identifier</code></td><td>Character encoding form, same as the database encoding</td></tr><tr><td><code class="literal">default_collate_catalog</code></td><td><code class="literal">sql_identifier</code></td><td>Name of the database containing the default collation (always the current database, if any collation is identified)</td></tr><tr><td><code class="literal">default_collate_schema</code></td><td><code class="literal">sql_identifier</code></td><td>Name of the schema containing the default collation</td></tr><tr><td><code class="literal">default_collate_name</code></td><td><code class="literal">sql_identifier</code></td><td>

  37.        Name of the default collation.  The default collation is

  38.        identified as the collation that matches

  39.        the <code class="literal">COLLATE</code> and <code class="literal">CTYPE</code>

  40.        settings of the current database.  If there is no such

  41.        collation, then this column and the associated schema and

  42.        catalog columns are null.

  43.       </td></tr></tbody></table></div></div><br class="table-break" /></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="infoschema-attributes.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="information-schema.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="infoschema-check-constraint-routine-usage.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">36.6. <code class="literal">attributes</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 36.8. <code class="literal">check_constraint_routine_usage</code></td></tr></table></div></body></html>
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