charset.sgml

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

         <entry><emphasis>ISO_8859_6</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>ISO_8859_7</literal></entry>
         <entry><emphasis>ISO_8859_7</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>ISO_8859_8</literal></entry>
         <entry><emphasis>ISO_8859_8</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>JOHAB</literal></entry>
         <entry><emphasis>JOHAB</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>KOI8</literal></entry>
         <entry><emphasis>KOI8</emphasis>,
         <literal>ISO_8859_5</literal>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>,
         <literal>WIN866</literal>,
         <literal>WIN1251</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN1</literal></entry>
         <entry><emphasis>LATIN1</emphasis>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN2</literal></entry>
         <entry><emphasis>LATIN2</emphasis>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>,
         <literal>WIN1250</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN3</literal></entry>
         <entry><emphasis>LATIN3</emphasis>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN4</literal></entry>
         <entry><emphasis>LATIN4</emphasis>,
         <literal>MULE_INTERNAL</literal>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN5</literal></entry>
         <entry><emphasis>LATIN5</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN6</literal></entry>
         <entry><emphasis>LATIN6</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN7</literal></entry>
         <entry><emphasis>LATIN7</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN8</literal></entry>
         <entry><emphasis>LATIN8</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN9</literal></entry>
         <entry><emphasis>LATIN9</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>LATIN10</literal></entry>
         <entry><emphasis>LATIN10</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>MULE_INTERNAL</literal></entry>
         <entry><emphasis>MULE_INTERNAL</emphasis>,
          <literal>BIG5</literal>,
          <literal>EUC_CN</literal>,
          <literal>EUC_JP</literal>,
          <literal>EUC_KR</literal>,
          <literal>EUC_TW</literal>,
          <literal>ISO_8859_5</literal>,
          <literal>KOI8</literal>,
          <literal>LATIN1</literal> to <literal>LATIN4</literal>,
          <literal>SJIS</literal>,
          <literal>WIN866</literal>,
          <literal>WIN1250</literal>,
          <literal>WIN1251</literal>
         </entry>
        </row>
        <row> 
         <entry><literal>SJIS</literal></entry>
         <entry><emphasis>not supported as a server encoding</emphasis>
         </entry>
        </row>
        <row>
         <entry><literal>SQL_ASCII</literal></entry>
         <entry><emphasis>any (no conversion will be performed)</emphasis>
         </entry>
        </row>
        <row>
         <entry><literal>UHC</literal></entry>
         <entry><emphasis>not supported as a server encoding</emphasis>
         </entry>
        </row>
        <row>
         <entry><literal>UTF8</literal></entry>
         <entry><emphasis>all supported encodings</emphasis>
         </entry>
        </row>
        <row>
         <entry><literal>WIN866</literal></entry>
         <entry><emphasis>WIN866</emphasis>,
          <literal>ISO_8859_5</literal>,
          <literal>KOI8</literal>,
          <literal>MULE_INTERNAL</literal>,
          <literal>UTF8</literal>,
          <literal>WIN1251</literal>
         </entry>
        </row>
        <row>
         <entry><literal>WIN874</literal></entry>
         <entry><emphasis>WIN874</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>WIN1250</literal></entry>
         <entry><emphasis>WIN1250</emphasis>,
          <literal>LATIN2</literal>,
          <literal>MULE_INTERNAL</literal>,
          <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>WIN1251</literal></entry>
         <entry><emphasis>WIN1251</emphasis>,
          <literal>ISO_8859_5</literal>,
          <literal>KOI8</literal>,
          <literal>MULE_INTERNAL</literal>,
          <literal>UTF8</literal>,
          <literal>WIN866</literal>
         </entry>
        </row>
        <row>
         <entry><literal>WIN1252</literal></entry>
         <entry><emphasis>WIN1252</emphasis>,
          <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>WIN1256</literal></entry>
         <entry><emphasis>WIN1256</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
        <row>
         <entry><literal>WIN1258</literal></entry>
         <entry><emphasis>WIN1258</emphasis>,
         <literal>UTF8</literal>
         </entry>
        </row>
       </tbody>
      </tgroup>
     </table>

    <para>
     To enable automatic character set conversion, you have to
     tell <productname>PostgreSQL</productname> the character set
     (encoding) you would like to use in the client. There are several
     ways to accomplish this:

     <itemizedlist>
      <listitem>
       <para>
        Using the <command>\encoding</command> command in
        <application>psql</application>.
        <command>\encoding</command> allows you to change client
        encoding on the fly. For
        example, to change the encoding to <literal>SJIS</literal>, type:

<programlisting>
\encoding SJIS
</programlisting>
       </para>
      </listitem>

      <listitem>
       <para>
        Using <application>libpq</> functions.
        <command>\encoding</command> actually calls
        <function>PQsetClientEncoding()</function> for its purpose.

<synopsis>
int PQsetClientEncoding(PGconn *<replaceable>conn</replaceable>, const char *<replaceable>encoding</replaceable>);
</synopsis>

        where <replaceable>conn</replaceable> is a connection to the server,
        and <replaceable>encoding</replaceable> is the encoding you
        want to use. If the function successfully sets the encoding, it returns 0,
        otherwise -1. The current encoding for this connection can be determined by
        using:

<synopsis>
int PQclientEncoding(const PGconn *<replaceable>conn</replaceable>);
</synopsis>

        Note that it returns the encoding ID, not a symbolic string
        such as <literal>EUC_JP</literal>. To convert an encoding ID to an encoding name, you
        can use:

<synopsis>
char *pg_encoding_to_char(int <replaceable>encoding_id</replaceable>);
</synopsis>
       </para>
      </listitem>

      <listitem>
       <para>
        Using <command>SET client_encoding TO</command>.

        Setting the client encoding can be done with this SQL command:

<programlisting>
SET CLIENT_ENCODING TO '<replaceable>value</>';
</programlisting>

        Also you can use the more standard SQL syntax <literal>SET NAMES</literal> for this purpose:

<programlisting>
SET NAMES '<replaceable>value</>';
</programlisting>

        To query the current client encoding:

<programlisting>
SHOW client_encoding;
</programlisting>

        To return to the default encoding:

<programlisting>
RESET client_encoding;
</programlisting>
       </para>
      </listitem>

      <listitem>
       <para>
        Using <envar>PGCLIENTENCODING</envar>. If the environment variable
        <envar>PGCLIENTENCODING</envar> is defined in the client's
        environment, that client encoding is automatically selected
        when a connection to the server is made.  (This can
        subsequently be overridden using any of the other methods
        mentioned above.)
       </para>
      </listitem>

      <listitem>
      <para>
       Using the configuration variable <xref
       linkend="guc-client-encoding">. If the
       <varname>client_encoding</> variable is set, that client
       encoding is automatically selected when a connection to the
       server is made.  (This can subsequently be overridden using any
       of the other methods mentioned above.)
       </para>
      </listitem>

     </itemizedlist>
    </para>

    <para>
     If the conversion of a particular character is not possible
     &mdash; suppose you chose <literal>EUC_JP</literal> for the
     server and <literal>LATIN1</literal> for the client, then some
     Japanese characters cannot be converted to
     <literal>LATIN1</literal> &mdash; it is transformed to its
     hexadecimal byte values in parentheses, e.g.,
     <literal>(826C)</literal>.
    </para>

    <para>
     If the client character set is defined as <literal>SQL_ASCII</>,
     encoding conversion is disabled, regardless of the server's character
     set.  Just as for the server, use of <literal>SQL_ASCII</> is unwise
     unless you are working with all-ASCII data.
    </para>
   </sect2>

   <sect2>
    <title>Further Reading</title>

    <para>
     These are good sources to start learning about various kinds of encoding
     systems.

     <variablelist>
      <varlistentry>
       <term><ulink url="http://www.i18ngurus.com/docs/984813247.html"></ulink></term>

       <listitem>
        <para>
         An extensive collection of documents about character sets, encodings,
         and code pages.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
       <term><ulink url="ftp://ftp.ora.com/pub/examples/nutshell/ujip/doc/cjk.inf"></ulink></term>

       <listitem>
        <para>
         Detailed explanations of <literal>EUC_JP</literal>,
         <literal>EUC_CN</literal>, <literal>EUC_KR</literal>,
         <literal>EUC_TW</literal> appear in section 3.2.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
       <term><ulink url="http://www.unicode.org/"></ulink></term>

       <listitem>
        <para>
         The web site of the Unicode Consortium
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
       <term>RFC 2044</term>

       <listitem>
        <para>
         <acronym>UTF</acronym>-8 is defined here.
        </para>
       </listitem>
      </varlistentry>
     </variablelist>
    </para>
   </sect2>

  </sect1>

</chapter>

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