<type>decimal</type>, <type>date</type>, <type>timestamp</type>,
     and <type>interval</type> types.  These data types cannot usefully be
     mapped to primitive host variable types (such
     as <type>int</type>, <type>long long int</type>,
     or <type>char[]</type>), because they have a complex internal
     structure.  Applications deal with these types by declaring host
     variables in special types and accessing them using functions in
     the pgtypes library.  The pgtypes library, described in detail
     in <xref linkend="ecpg-pgtypes"/> contains basic functions to deal
     with those types, such that you do not need to send a query to
     the SQL server just for adding an interval to a time stamp for
     example.
    </para>

    <para>
     The follow subsections describe these special data types. For
     more details about pgtypes library functions,
     see <xref linkend="ecpg-pgtypes"/>.
    </para>

    <sect4 id="ecpg-special-types-timestamp-date">
     <title>timestamp, date</title>

     <para>
      Here is a pattern for handling <type>timestamp</type> variables
      in the ECPG host application.
     </para>

     <para>
      First, the program has to include the header file for the
      <type>timestamp</type> type:
<programlisting>
#include &lt;pgtypes_timestamp.h>
</programlisting>
     </para>

     <para>
      Next, declare a host variable as type <type>timestamp</type> in
      the declare section:
<programlisting>
EXEC SQL BEGIN DECLARE SECTION;
timestamp ts;
EXEC SQL END DECLARE SECTION;
</programlisting>
     </para>

     <para>
      And after reading a value into the host variable, process it
      using pgtypes library functions. In following example, the
      <type>timestamp</type> value is converted into text (ASCII) form
      with the <function>PGTYPEStimestamp_to_asc()</function>
      function:
<programlisting>
EXEC SQL SELECT now()::timestamp INTO :ts;

printf("ts = %s\n", PGTYPEStimestamp_to_asc(ts));
</programlisting>
      This example will show some result like following:
<screen>
ts = 2010-06-27 18:03:56.949343
</screen>
     </para>

     <para>
      In addition, the DATE type can be handled in the same way. The
      program has to include <filename>pgtypes_date.h</filename>, declare a host variable
      as the date type and convert a DATE value into a text form using
      <function>PGTYPESdate_to_asc()</function> function. For more details about the
      pgtypes library functions, see <xref linkend="ecpg-pgtypes"/>.
     </para>
    </sect4>

    <sect4 id="ecpg-type-interval">
     <title>interval</title>

     <para>
      The handling of the <type>interval</type> type is also similar
      to the <type>timestamp</type> and <type>date</type> types.  It
      is required, however, to allocate memory for
      an <type>interval</type> type value explicitly.  In other words,
      the memory space for the variable has to be allocated in the
      heap memory, not in the stack memory.
     </para>

     <para>
      Here is an example program:
<programlisting>
#include &lt;stdio.h>
#include &lt;stdlib.h>
#include &lt;pgtypes_interval.h>

int
main(void)
{
EXEC SQL BEGIN DECLARE SECTION;
    interval *in;
EXEC SQL END DECLARE SECTION;

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

    in = PGTYPESinterval_new();
    EXEC SQL SELECT '1 min'::interval INTO :in;
    printf("interval = %s\n", PGTYPESinterval_to_asc(in));
    PGTYPESinterval_free(in);

    EXEC SQL COMMIT;
    EXEC SQL DISCONNECT ALL;
    return 0;
}
</programlisting>
     </para>
    </sect4>

    <sect4 id="ecpg-type-numeric-decimal">
     <title>numeric, decimal</title>

     <para>
      The handling of the <type>numeric</type>
      and <type>decimal</type> types is similar to the
      <type>interval</type> type: It requires defining a pointer,
      allocating some memory space on the heap, and accessing the
      variable using