153 lines
3.8 KiB
Plaintext
153 lines
3.8 KiB
Plaintext
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$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.9 2002/03/04 18:50:20 momjian Exp $
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<chapter id="pgeasy">
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<title><application>libpgeasy</application> - Simplified C Library</title>
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<note>
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<title>Author</title>
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<para>
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Written by Bruce Momjian
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(<email>pgman@candle.pha.pa.us</email>)
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and last updated 2002-03-04
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</para>
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</note>
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<para>
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<application>pgeasy</application> allows you to cleanly interface
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to the <application>libpq</application> library, more like a 4GL
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SQL interface. Refer to <xref linkend="libpq"> for more
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information about <application>libpq</application>.
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</para>
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<para>
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It consists of a set of simplified C functions that encapsulate the
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functionality of <application>libpq</application>. The functions are:
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<itemizedlist>
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<listitem>
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<synopsis>
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PGresult *doquery(char *query);
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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PGconn *connectdb(char *options);
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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void disconnectdb();
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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int fetch(void *param,...);
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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int fetchwithnulls(void *param,...);
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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void reset_fetch();
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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void on_error_continue();
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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void on_error_stop();
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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PGresult *get_result();
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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void set_result(PGresult *newres);
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</synopsis>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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Many functions return a structure or value, so you can work
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with the result if required.
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</para>
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<para>
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You basically connect to the database with
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<function>connectdb</function>, issue your query with
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<function>doquery</function>, fetch the results with
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<function>fetch</function>, and finish with
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<function>disconnectdb</function>.
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</para>
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<para>
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For <literal>SELECT</literal> queries, <function>fetch</function>
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allows you to pass pointers as parameters, and on return the
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variables are filled with data from the binary cursor you opened.
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These binary cursors cannot be used if you are running the
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<application>pgeasy</application> client on a system with a different
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architecture than the database server. If you pass a NULL pointer
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parameter, the column is skipped. <function>fetchwithnulls</function>
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allows you to retrieve the NULL status of the field by passing an
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<literal>int*</literal> after each result pointer, which returns true
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or false to indicate if the field is null. You can always use
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<application>libpq</application> functions on the
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<structname>PGresult</structname> pointer returned by
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<function>doquery</function>. <function>reset_fetch</function> starts
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the fetch back at the beginning.
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</para>
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<para>
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<function>get_result</function> and <function>set_result</function>
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allow you to handle multiple open result sets. Use
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<function>get_result</function> to save a result into an application
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variable. You can then later use <function>set_result</function> to
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return to the previously save result.
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</para>
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<para>
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There are several demonstration programs in
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<filename>pgsql/src/interfaces/libpgeasy/examples</>.
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</para>
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</chapter>
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