directly into the C source code, but there is a
   facility that allows you to call arbitrary SQL statements that you
   provide in a string variable.
  </para>

  <sect2 id="ecpg-dynamic-without-result">
   <title>Executing Statements without a Result Set</title>

   <para>
    The simplest way to execute an arbitrary SQL statement is to use
    the command <command>EXECUTE IMMEDIATE</command>.  For example:
<programlisting>
EXEC SQL BEGIN DECLARE SECTION;
const char *stmt = "CREATE TABLE test1 (...);";
EXEC SQL END DECLARE SECTION;

EXEC SQL EXECUTE IMMEDIATE :stmt;
</programlisting>
    <command>EXECUTE IMMEDIATE</command> can be used for SQL
    statements that do not return a result set (e.g.,
    DDL, <command>INSERT</command>, <command>UPDATE</command>,
    <command>DELETE</command>).  You cannot execute statements that
    retrieve data (e.g., <command>SELECT</command>) this way.  The
    next section describes how to do that.
   </para>
  </sect2>

  <sect2 id="ecpg-dynamic-input">
   <title>Executing a Statement with Input Parameters</title>

   <para>
    A more powerful way to execute arbitrary SQL statements is to
    prepare them once and execute the prepared statement as often as
    you like.  It is also possible to prepare a generalized version of
    a statement and then execute specific versions of it by
    substituting parameters.  When preparing the statement, write
    question marks where you want to substitute parameters later.  For
    example:
<programlisting>
EXEC SQL BEGIN DECLARE SECTION;
const char *stmt = "INSERT INTO test1 VALUES(?, ?);";
EXEC SQL END DECLARE SECTION;

EXEC SQL PREPARE mystmt FROM :stmt;
 ...
EXEC SQL EXECUTE mystmt USING 42, 'foobar';
</programlisting>
   </para>

   <para>
    When you don't need the prepared statement anymore, you should
    deallocate it:
<programlisting>
EXEC SQL DEALLOCATE PREPARE <replaceable>name</replaceable>;
</programlisting>
   </para>
  </sect2>

  <sect2 id="ecpg-dynamic-with-result">
   <title>Executing a Statement with a Result Set</title>

   <para>
    To execute an SQL statement with a single result row,
    <command>EXECUTE</command> can be used.  To save the result, add
    an <literal>INTO</literal> clause.
<programlisting><![CDATA[
EXEC SQL BEGIN DECLARE SECTION;
const char *stmt = "SELECT a, b, c FROM test1 WHERE a > ?";
int v1, v2;
VARCHAR v3[50];
EXEC SQL END DECLARE SECTION;

EXEC SQL PREPARE mystmt FROM :stmt;
 ...
EXEC SQL EXECUTE mystmt INTO :v1, :v2, :v3 USING 37;
]]>
</programlisting>
    An <command>EXECUTE</command> command can have an
    <literal>INTO</literal> clause, a <literal>USING</literal> clause,
    both, or neither.
   </para>

   <para>
    If a query is expected to return more than one result row, a
    cursor should be used, as in the following example.
    (See <xref linkend="ecpg-cursors"/> for more details about the
    cursor.)
<programlisting>
EXEC SQL BEGIN DECLARE SECTION;
char dbaname[128];
char datname[128];
char *stmt = "SELECT u.usename as dbaname, d.datname "
             "  FROM pg_database d, pg_user u "
             "  WHERE d.datdba = u.usesysid";
EXEC SQL END DECLARE SECTION;

EXEC SQL CONNECT TO testdb AS con1 USER testuser;
EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;

EXEC SQL PREPARE stmt1 FROM :stmt;

EXEC SQL DECLARE cursor1 CURSOR FOR stmt1;
EXEC SQL OPEN cursor1;

EXEC SQL WHENEVER NOT FOUND DO BREAK;

while (1)
{
    EXEC SQL FETCH cursor1 INTO :dbaname,:datname;
    printf("dbaname=%s, datname=%s\n", dbaname, datname);
}

EXEC SQL CLOSE cursor1;

EXEC SQL COMMIT;
EXEC SQL DISCONNECT ALL;
</programlisting>
   </para>
  </sect2>
 </sect1>

 <sect1 id="ecpg-pgtypes">
  <title>pgtypes Library</title>

  <para>
   The pgtypes library maps <productname>PostgreSQL</productname> database
   types to C equivalents that can be used in C programs. It also offers
   functions to do basic calculations with those types within C, i.e., without
   the help of the <productname>PostgreSQL</productname>