charset.sgml

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

        </row>
        <row>
         <entry><literal>ISO_8859_5</literal></entry>
         <entry>ISO 8859-5, <acronym>ECMA</> 113</entry>
         <entry>Latin/Cyrillic</entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>ISO_8859_6</literal></entry>
         <entry>ISO 8859-6, <acronym>ECMA</> 114</entry>
         <entry>Latin/Arabic</entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>ISO_8859_7</literal></entry>
         <entry>ISO 8859-7, <acronym>ECMA</> 118</entry>
         <entry>Latin/Greek</entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>ISO_8859_8</literal></entry>
         <entry>ISO 8859-8, <acronym>ECMA</> 121</entry>
         <entry>Latin/Hebrew</entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>JOHAB</literal></entry>
         <entry><acronym>JOHAB</></entry>
         <entry>Korean (Hangul)</entry>
         <entry>1-3</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>KOI8</literal></entry>
         <entry><acronym>KOI</acronym>8-R(U)</entry>
         <entry>Cyrillic</entry>
         <entry>1</entry>
         <entry><literal>KOI8R</></entry>
        </row>
        <row>
         <entry><literal>LATIN1</literal></entry>
         <entry>ISO 8859-1, <acronym>ECMA</> 94</entry>
         <entry>Western European</entry>
         <entry>1</entry>
         <entry><literal>ISO88591</></entry>
        </row>
        <row>
         <entry><literal>LATIN2</literal></entry>
         <entry>ISO 8859-2, <acronym>ECMA</> 94</entry>
         <entry>Central European</entry>
         <entry>1</entry>
         <entry><literal>ISO88592</></entry>
        </row>
        <row>
         <entry><literal>LATIN3</literal></entry>
         <entry>ISO 8859-3, <acronym>ECMA</> 94</entry>
         <entry>South European</entry>
         <entry>1</entry>
         <entry><literal>ISO88593</></entry>
        </row>
        <row>
         <entry><literal>LATIN4</literal></entry>
         <entry>ISO 8859-4, <acronym>ECMA</> 94</entry>
         <entry>North European</entry>
         <entry>1</entry>
         <entry><literal>ISO88594</></entry>
        </row>
        <row>
         <entry><literal>LATIN5</literal></entry>
         <entry>ISO 8859-9, <acronym>ECMA</> 128</entry>
         <entry>Turkish</entry>
         <entry>1</entry>
         <entry><literal>ISO88599</></entry>
        </row>
        <row>
         <entry><literal>LATIN6</literal></entry>
         <entry>ISO 8859-10, <acronym>ECMA</> 144</entry>
         <entry>Nordic</entry>
         <entry>1</entry>
         <entry><literal>ISO885910</></entry>
        </row>
        <row>
         <entry><literal>LATIN7</literal></entry>
         <entry>ISO 8859-13</entry>
         <entry>Baltic</entry>
         <entry>1</entry>
         <entry><literal>ISO885913</></entry>
        </row>
        <row>
         <entry><literal>LATIN8</literal></entry>
         <entry>ISO 8859-14</entry>
         <entry>Celtic</entry>
         <entry>1</entry>
         <entry><literal>ISO885914</></entry>
        </row>
        <row>
         <entry><literal>LATIN9</literal></entry>
         <entry>ISO 8859-15</entry>
         <entry>LATIN1 with Euro and accents</entry>
         <entry>1</entry>
         <entry>ISO885915</entry>
        </row>
        <row>
         <entry><literal>LATIN10</literal></entry>
         <entry>ISO 8859-16, <acronym>ASRO</> SR 14111</entry>
         <entry>Romanian</entry>
         <entry>1</entry>
         <entry><literal>ISO885916</></entry>
        </row>
        <row>
         <entry><literal>MULE_INTERNAL</literal></entry>
         <entry>Mule internal code</entry>
         <entry>Multilingual Emacs</entry>
         <entry>1-4</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>SJIS</literal></entry>
         <entry>Shift JIS</entry>
         <entry>Japanese</entry>
         <entry>1-2</entry>
         <entry><literal>Mskanji</>, <literal>ShiftJIS</>, <literal>WIN932</>, <literal>Windows932</></entry>
        </row>
        <row>
         <entry><literal>SQL_ASCII</literal></entry>
         <entry>unspecified (see text)</entry>
         <entry><emphasis>any</></entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>UHC</literal></entry>
         <entry>Unified Hangul Code</entry>
         <entry>Korean</entry>
         <entry>1-2</entry>
         <entry><literal>WIN949</>, <literal>Windows949</></entry>
        </row>
        <row>
         <entry><literal>UTF8</literal></entry>
         <entry>Unicode, 8-bit</entry>
         <entry><emphasis>all</></entry>
         <entry>1-4</entry>
         <entry><literal>Unicode</></entry>
        </row>
        <row>
         <entry><literal>WIN866</literal></entry>
         <entry>Windows CP866</entry>
         <entry>Cyrillic</entry>
         <entry>1</entry>
         <entry><literal>ALT</></entry>
        </row>
        <row>
         <entry><literal>WIN874</literal></entry>
         <entry>Windows CP874</entry>
         <entry>Thai</entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>WIN1250</literal></entry>
         <entry>Windows CP1250</entry>
         <entry>Central European</entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>WIN1251</literal></entry>
         <entry>Windows CP1251</entry>
         <entry>Cyrillic</entry>
         <entry>1</entry>
         <entry><literal>WIN</></entry>
        </row>
        <row>
         <entry><literal>WIN1252</literal></entry>
         <entry>Windows CP1252</entry>
         <entry>Western European</entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>WIN1256</literal></entry>
         <entry>Windows CP1256</entry>
         <entry>Arabic</entry>
         <entry>1</entry>
         <entry></entry>
        </row>
        <row>
         <entry><literal>WIN1258</literal></entry>
         <entry>Windows CP1258</entry>
         <entry>Vietnamese</entry>
         <entry>1</entry>
         <entry><literal>ABC</>, <literal>TCVN</>, <literal>TCVN5712</>, <literal>VSCII</></entry>
        </row>
       </tbody>
      </tgroup>
     </table>

     <para>
      Not all <acronym>API</>s support all the listed character sets. For example, the
      <productname>PostgreSQL</>
      JDBC driver does not support <literal>MULE_INTERNAL</>, <literal>LATIN6</>,
      <literal>LATIN8</>, and <literal>LATIN10</>.
     </para>

     <para>
      The <literal>SQL_ASCII</> setting behaves considerably differently
      from the other settings.  When the server character set is
      <literal>SQL_ASCII</>, the server interprets byte values 0-127
      according to the ASCII standard, while byte values 128-255 are taken
      as uninterpreted characters.  No encoding conversion will be done when
      the setting is <literal>SQL_ASCII</>.  Thus, this setting is not so
      much a declaration that a specific encoding is in use, as a declaration
      of ignorance about the encoding.  In most cases, if you are
      working with any non-ASCII data, it is unwise to use the
      <literal>SQL_ASCII</> setting, because
      <productname>PostgreSQL</productname> will be unable to help you by
      converting or validating non-ASCII characters.
     </para>
    </sect2>
    
   <sect2>
    <title>Setting the Character Set</title>

    <para>
     <command>initdb</> defines the default character set
     for a <productname>PostgreSQL</productname> cluster. For example,

<screen>
initdb -E EUC_JP
</screen>

     sets the default character set (encoding) to
     <literal>EUC_JP</literal> (Extended Unix Code for Japanese).  You
     can use <option>--encoding</option> instead of
     <option>-E</option> if you prefer to type longer option strings.
     If no <option>-E</> or <option>--encoding</option> option is
     given, <command>initdb</> attempts to determine the appropriate
     encoding to use based on the specified or default locale.
    </para>

    <para>
     You can create a database with a different character set:

<screen>
createdb -E EUC_KR korean
</screen>

     This will create a database named <literal>korean</literal> that
     uses the character set <literal>EUC_KR</literal>.  Another way to
     accomplish this is to use this SQL command:

<programlisting>
CREATE DATABASE korean WITH ENCODING 'EUC_KR';
</programlisting>

     The encoding for a database is stored in the system catalog
     <literal>pg_database</literal>.  You can see that by using the
     <option>-l</option> option or the <command>\l</command> command
     of <command>psql</command>.

<screen>
$ <userinput>psql -l</userinput>
            List of databases
   Database    |  Owner  |   Encoding    
---------------+---------+---------------
 euc_cn        | t-ishii | EUC_CN
 euc_jp        | t-ishii | EUC_JP
 euc_kr        | t-ishii | EUC_KR
 euc_tw        | t-ishii | EUC_TW
 mule_internal | t-ishii | MULE_INTERNAL
 postgres      | t-ishii | EUC_JP
 regression    | t-ishii | SQL_ASCII
 template1     | t-ishii | EUC_JP
 test          | t-ishii | EUC_JP
 utf8          | t-ishii | UTF8
(9 rows)
</screen>
    </para>

    <important>
     <para>
      Although you can specify any encoding you want for a database, it is
      unwise to choose an encoding that is not what is expected by the locale
      you have selected.  The <literal>LC_COLLATE</literal> and
      <literal>LC_CTYPE</literal> settings imply a particular encoding,
      and locale-dependent operations (such as sorting) are likely to
      misinterpret data that is in an incompatible encoding.
     </para>

     <para>
      Since these locale settings are frozen by <command>initdb</>, the
      apparent flexibility to use different encodings in different databases
      of a cluster is more theoretical than real.  It is likely that these
      mechanisms will be revisited in future versions of
      <productname>PostgreSQL</productname>.
     </para>

     <para>
      One way to use multiple encodings safely is to set the locale to
      <literal>C</> or <literal>POSIX</> during <command>initdb</>, thus
      disabling any real locale awareness.
     </para>
    </important>
   </sect2>

   <sect2>
    <title>Automatic Character Set Conversion Between Server and Client</title>

    <para>
     <productname>PostgreSQL</productname> supports automatic
     character set conversion between server and client for certain
     character sets. The conversion information is stored in the
     <literal>pg_conversion</> system catalog. You can create a new
     conversion by using the SQL command <command>CREATE
     CONVERSION</command>. <productname>PostgreSQL</> comes with some
     predefined conversions. They are listed in <xref
     linkend="multibyte-translation-table">.
    </para>

     <table id="multibyte-translation-table">
      <title>Client/Server Character Set Conversions</title>
      <tgroup cols="2">
       <thead>
        <row>
         <entry>Server Character Set</entry>
         <entry>Available Client Character Sets</entry>
        </row>
       </thead>
       <tbody>
        <row>
         <entry><literal>BIG5</literal></entry>
         <entry><emphasis>not supported as a server encoding</emphasis>
         </entry>
        </row>
        <row>
         <entry><literal>EUC_CN</literal></entry>
         <entry><emphasis>EUC_CN</emphasis>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>EUC_JP</literal></entry>
         <entry><emphasis>EUC_JP</emphasis>,
         <literal>MULE_INTERNAL</literal>,
         <literal>SJIS</literal>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>EUC_KR</literal></entry>
         <entry><emphasis>EUC_KR</emphasis>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>EUC_TW</literal></entry>
         <entry><emphasis>EUC_TW</emphasis>,
         <literal>BIG5</literal>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>GB18030</literal></entry>
         <entry><emphasis>not supported as a server encoding</emphasis>
         </entry>
        </row>
        <row>
         <entry><literal>GBK</literal></entry>
         <entry><emphasis>not supported as a server encoding</emphasis>
         </entry>
        </row>
        <row>
         <entry><literal>ISO_8859_5</literal></entry>
         <entry><emphasis>ISO_8859_5</emphasis>,
         <literal>KOI8</literal>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>,
         <literal>WIN866</literal>,
         <literal>WIN1251</literal>
         </entry>
        </row>
        <row>
         <entry><literal>ISO_8859_6</literal></entry>