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<!--
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.6 2001/09/10 21:58:46 petere Exp $
-->
<chapter id="pgeasy-chapter">
<title id="pgeasy"><application>libpgeasy</application> - Simplified C Library</title>
<note>
<title>Author</title>
<para>
Written by Bruce Momjian
(<email>pgman@candle.pha.pa.us</email>)
and last updated 2000-03-30
</para>
</note>
<para>
<productname>pgeasy</productname> allows you to cleanly interface
to the <productname>libpq</productname> library,
more like a 4GL SQL interface.
</para>
<para>
It consists of set of simplified C functions that encapsulate the
functionality of <application>libpq</application>.
The functions are:
<itemizedlist>
<listitem>
<synopsis>
PGresult *doquery(char *query);
</synopsis>
</listitem>
<listitem>
<synopsis>
PGconn *connectdb(char *options);
</synopsis>
</listitem>
<listitem>
<synopsis>
void disconnectdb();
</synopsis>
</listitem>
<listitem>
<synopsis>
int fetch(void *param,...);
</synopsis>
</listitem>
<listitem>
<synopsis>
int fetchwithnulls(void *param,...);
</synopsis>
</listitem>
<listitem>
<synopsis>
void reset_fetch();
</synopsis>
</listitem>
<listitem>
<synopsis>
void on_error_continue();
</synopsis>
</listitem>
<listitem>
<synopsis>
void on_error_stop();
</synopsis>
</listitem>
<listitem>
<synopsis>
PGresult *get_result();
</synopsis>
</listitem>
<listitem>
<synopsis>
void set_result(PGresult *newres);
</synopsis>
</listitem>
<listitem>
<synopsis>
void unset_result(PGresult *oldres);
</synopsis>
</listitem>
</itemizedlist>
</para>
<para>
Many functions return a structure or value, so you can do more work
with the result if required.
</para>
<para>
You basically connect to the database with <function>connectdb</function>,
issue your query with <function>doquery</function>,
fetch the results with <function>fetch</function>,
and finish with <function>disconnectdb</function>.
</para>
<para>
For <literal>SELECT</literal> queries, <function>fetch</function>
allows you to pass pointers as parameters, and on return the variables
are filled with data from the binary cursor you opened. These binary
cursors can not be used if you are running the
<productname>pgeasy</productname>
client on a system with a different architecture than the database
server. If you pass a NULL pointer parameter, the column is skipped.
<function>fetchwithnulls</function> allows you to retrieve the NULL
status of the field by passing an <literal>int*</literal>
after each result pointer, which returns true or false if the field is null.
You can always use <application>libpq</application> functions on the <structname>PGresult</structname> pointer returned
by <function>doquery</function>.
<function>reset_fetch</function> starts the fetch back at the beginning.
</para>
<para>
<function>get_result</function>,
<function>set_result</function>,
and
<function>unset_result</function>
allow you to handle multiple result sets at the same time.
</para>
<para>
There are a variety of demonstration programs in the
source directory.
</para>
</chapter>
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