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427 lines
11 KiB
Plaintext
427 lines
11 KiB
Plaintext
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/ecpg-ref.sgml,v 1.19 2002/04/21 19:02:39 thomas Exp $
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PostgreSQL documentation
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-->
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<refentry id="APP-ECPG">
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<refmeta>
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<refentrytitle id="app-ecpg-title"><application>ecpg</application></refentrytitle>
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<manvolnum>1</manvolnum>
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<refmiscinfo>Application</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>
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<application>ecpg</application>
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</refname>
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<refpurpose>
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embedded SQL C preprocessor
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</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<refsynopsisdivinfo>
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<date>1999-07-20</date>
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</refsynopsisdivinfo>
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<cmdsynopsis>
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<command>ecpg</command>
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<arg choice="opt">-v</arg>
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<arg choice="opt">-t</arg>
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<arg choice="opt">-I <replaceable>include-path</replaceable></arg>
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<arg choice="opt">-o <replaceable>outfile</replaceable></arg>
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<arg choice="plain" rep="repeat"><replaceable>file</replaceable></arg>
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</cmdsynopsis>
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<refsect2 id="R2-APP-ECPG-1">
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<refsect2info>
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<date>1999-07-20</date>
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</refsect2info>
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<title>
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Inputs
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</title>
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<para>
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<application>ecpg</application> accepts the following command
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line arguments:
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<variablelist>
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<varlistentry>
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<term>-v</term>
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<listitem>
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<para>
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Print version information.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>-t</term>
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<listitem>
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<para>
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Turn on auto-commit of transactions. In this mode, each query is
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automatically committed unless it is inside an explicit
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transaction block. In the default mode, queries are committed
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only when <command>exec sql commit</command> is issued.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>-I <replaceable class="parameter">include-path</replaceable></term>
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<listitem>
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<para>
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Specify an additional include path.
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Defaults are <filename>.</filename> (current directory),
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<filename>/usr/local/include</filename>, the
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<productname>PostgreSQL</productname> include path which is
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defined at compile time (default:
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<filename>/usr/local/pgsql/include</filename>), and
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<filename>/usr/include</filename>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>-o <replaceable>outfile</replaceable></term>
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<listitem>
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<para>
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Specifies that <application>ecpg</application> should write all its output to <replaceable>outfile</replaceable>.
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If no such option is given the output is written to
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<filename><replaceable>name</replaceable>.c</filename>,
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assuming the input file was
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named <filename><replaceable>name</replaceable>.pgc</filename>.
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If the input file does have the expected
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<literal>.pgc</literal> suffix, then the output file will have
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<literal>.pgc</literal> appended to the input file name.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">file</replaceable></term>
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<listitem>
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<para>
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The files to be processed.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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<refsect2 id="R2-APP-ECPG-2">
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<refsect2info>
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<date>1998-11-05</date>
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</refsect2info>
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<title>
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Outputs
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</title>
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<para>
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<application>ecpg</application> will create a file or
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write to <filename>stdout</filename>.
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<variablelist>
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<varlistentry>
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<term>Return value</term>
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<listitem>
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<para>
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<application>ecpg</application> returns 0 to the shell on successful completion, non-zero
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for errors.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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</refsynopsisdiv>
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<refsect1 id="R1-APP-ECPG-description">
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<title>Description</title>
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<para>
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<application>ecpg</application>
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is an embedded SQL preprocessor for the C language and the
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<productname>PostgreSQL</productname>. It
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enables development of C programs with embedded SQL code.
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</para>
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<para>
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Linus Tolke (<email>linus@epact.se</email>) was the
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original author of <application>ecpg</application> (up to version 0.2).
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Michael Meskes (<email>meskes@debian.org</email>)
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is the current author and maintainer of <application>ecpg</application>.
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Thomas Good (<email>tomg@q8.nrnet.org</email>)
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is the author of the last revision of the <application>ecpg</application> man page, on which
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this document is based.
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</para>
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</refsect1>
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<refsect1 id="R1-APP-ECPG-2">
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<title>Usage</title>
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<refsect2 id="R2-APP-ECPG-preprocessing">
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<title>Preprocessing for Compilation</title>
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<para>
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An embedded SQL source file must be preprocessed before
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compilation:
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<synopsis>
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ecpg [ -d ] [ -o <replaceable>file</replaceable> ] <replaceable>file</replaceable>.pgc
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</synopsis>
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where the optional <option>-d</option> flag turns on debugging.
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The <literal>.pgc</literal> extension is an
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arbitrary means of denoting <application>ecpg</application> source.
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</para>
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<para>
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You may want to redirect the preprocessor output to a log file.
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</para>
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</refsect2>
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<refsect2 id="R2-APP-ECPG-compiling">
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<title>Compiling and Linking</title>
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<para>
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Assuming the <productname>PostgreSQL</productname> binaries are in
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<filename>/usr/local/pgsql</filename>, you will need to compile
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and link your preprocessed source file:
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<synopsis>
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gcc -g -I /usr/local/pgsql/include [ -o <replaceable>file</replaceable> ] <replaceable>file</replaceable>.c -L /usr/local/pgsql/lib -lecpg -lpq
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</synopsis>
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</para>
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</refsect2>
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</refsect1>
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<refsect1 id="R1-APP-ECPG-grammar">
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<title>Grammar</title>
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<refsect2 id="R2-APP-ECPG-library">
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<title>Libraries</title>
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<para>
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The preprocessor will prepend two directives to the source:
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<programlisting>
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#include <ecpgtype.h>
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#include <ecpglib.h>
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</programlisting>
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</para>
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</refsect2>
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<refsect2 id="R2-APP-declaration">
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<title>Variable Declaration</title>
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<para>
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Variables declared within <application>ecpg</application> source code must be prepended with:
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<programlisting>
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EXEC SQL BEGIN DECLARE SECTION;
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</programlisting>
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</para>
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<para>
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Similarly, variable declaration sections must terminate with:
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<programlisting>
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EXEC SQL END DECLARE SECTION;
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</programlisting>
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<note>
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<para>
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Prior to version 2.1.0, each variable had to be declared
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on a separate line. As of version 2.1.0 multiple variables may
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be declared on a single line:
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<programlisting>
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char foo[16], bar[16];
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</programlisting>
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</para>
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</note>
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</para>
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</refsect2>
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<refsect2 id="R2-APP-ECPG-errors">
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<title>Error Handling</title>
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<para>
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The SQL communication area is defined with:
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<programlisting>
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EXEC SQL INCLUDE sqlca;
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</programlisting>
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</para>
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<note>
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<para>
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The <literal>sqlca</literal> is in lowercase.
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While SQL convention may be
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followed, i.e., using uppercase to separate embedded SQL
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from C statements, <literal>sqlca</literal> (which includes the <filename>sqlca.h</>
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header file) <emphasis>must</> be lowercase. This is because the
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EXEC SQL prefix indicates that this inclusion will be parsed by
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<application>ecpg</application>.
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<application>ecpg</application> observes case sensitivity
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(<filename>SQLCA.h</> will not be found).
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<command>EXEC SQL INCLUDE</command>
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can be used to include other header files
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as long as case sensitivity is observed.
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</para>
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</note>
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<para>
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The <literal>sqlprint</literal> command is used with the <literal>EXEC SQL WHENEVER</literal>
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statement to turn on error handling throughout the
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program:
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<programlisting>
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EXEC SQL WHENEVER sqlerror sqlprint;
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</programlisting>
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and
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<programlisting>
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EXEC SQL WHENEVER not found sqlprint;
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</programlisting>
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</para>
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<note>
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<para>
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This is <emphasis>not</emphasis> an exhaustive example of usage for
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the <command>EXEC SQL WHENEVER</command> statement.
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Further examples of usage may
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be found in SQL manuals (e.g., <citetitle>The LAN TIMES Guide to SQL</> by
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Groff and Weinberg).
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</para>
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</note>
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</refsect2>
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<refsect2 id="R2-APP-ECPG-connecting">
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<title>Connecting to the Database Server</title>
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<para>
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One connects to a database using the following:
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<programlisting>
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EXEC SQL CONNECT TO <replaceable>dbname</replaceable>;
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</programlisting>
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where the database name is not quoted. Prior to version 2.1.0, the
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database name was required to be inside single quotes.
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</para>
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<para>
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Specifying a server and port name in the connect statement is also
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possible. The syntax is:
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<synopsis>
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<replaceable>dbname</replaceable>[@<replaceable>server</replaceable>][:<replaceable>port</replaceable>]
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</synopsis>
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or
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<synopsis>
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<tcp|unix>:postgresql://<replaceable>server</replaceable>[:<replaceable>port</replaceable>][/<replaceable>dbname</replaceable>][?<replaceable>options</replaceable>]
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</synopsis>
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</para>
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</refsect2>
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<refsect2 id="R2-APP-ECPG-queries">
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<title>Queries</title>
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<para>
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In general, SQL queries acceptable to other applications such as
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<application>psql</application> can be embedded into your C
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code. Here are some examples of how to do that.
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</para>
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<para>
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Create Table:
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<programlisting>
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EXEC SQL CREATE TABLE foo (number int4, ascii char(16));
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EXEC SQL CREATE UNIQUE index num1 on foo(number);
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EXEC SQL COMMIT;
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</programlisting>
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</para>
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<para>
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Insert:
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<programlisting>
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EXEC SQL INSERT INTO foo (number, ascii) VALUES (9999, 'doodad');
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EXEC SQL COMMIT;
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</programlisting>
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</para>
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<para>
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Delete:
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<programlisting>
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EXEC SQL DELETE FROM foo WHERE number = 9999;
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EXEC SQL COMMIT;
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</programlisting>
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</para>
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<para>
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Singleton Select:
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<programlisting>
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EXEC SQL SELECT foo INTO :FooBar FROM table1 WHERE ascii = 'doodad';
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</programlisting>
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</para>
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<para>
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Select using Cursors:
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<programlisting>
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EXEC SQL DECLARE foo_bar CURSOR FOR
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SELECT number, ascii FROM foo
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ORDER BY ascii;
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EXEC SQL FETCH foo_bar INTO :FooBar, DooDad;
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...
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EXEC SQL CLOSE foo_bar;
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EXEC SQL COMMIT;
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</programlisting>
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</para>
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<para>
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Updates:
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<programlisting>
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EXEC SQL UPDATE foo
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SET ascii = 'foobar'
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WHERE number = 9999;
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EXEC SQL COMMIT;
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</programlisting>
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</para>
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</refsect2>
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</refsect1>
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<refsect1 id="R1-APP-ECPG-notes">
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<title>Notes</title>
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<para>
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The complete structure definition MUST be listed
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inside the declare section.
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</para>
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<para>
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See the <filename>TODO</filename> file in the source for some more
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missing features.
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:nil
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"../reference.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:"/usr/lib/sgml/catalog"
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sgml-local-ecat-files:nil
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End:
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-->
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