structure.</simpara></step>
     <step><simpara>Repeat above as you need.</simpara></step>
    </procedure>

    <para>
     Here is an example retrieving a result set through an SQLDA.
    </para>

    <para>
     First, declare a <type>sqlda_t</type> structure to receive the result set.
<programlisting>
sqlda_t *sqlda1;
</programlisting>
    </para>

    <para>
     Next, specify the SQLDA in a command.  This is
     a <command>FETCH</command> command example.
<programlisting>
EXEC SQL FETCH NEXT FROM cur1 INTO DESCRIPTOR sqlda1;
</programlisting>
    </para>

    <para>
     Run a loop following the linked list to retrieve the rows.
<programlisting>
sqlda_t *cur_sqlda;

for (cur_sqlda = sqlda1;
     cur_sqlda != NULL;
     cur_sqlda = cur_sqlda->desc_next)
{
    ...
}
</programlisting>
    </para>

    <para>
     Inside the loop, run another loop to retrieve each column data
     (<type>sqlvar_t</type> structure) of the row.
<programlisting>
for (i = 0; i &lt; cur_sqlda->sqld; i++)
{
    sqlvar_t v = cur_sqlda->sqlvar[i];
    char *sqldata = v.sqldata;
    short sqllen  = v.sqllen;
    ...
}
</programlisting>
    </para>

    <para>
     To get a column value, check the <structfield>sqltype</structfield> value,
     a member of the <type>sqlvar_t</type> structure.  Then, switch
     to an appropriate way, depending on the column type, to copy
     data from the <structfield>sqlvar</structfield> field to a host variable.
<programlisting>
char var_buf[1024];

switch (v.sqltype)
{
    case ECPGt_char:
        memset(&amp;var_buf, 0, sizeof(var_buf));
        memcpy(&amp;var_buf, sqldata, (sizeof(var_buf) &lt;= sqllen ? sizeof(var_buf) - 1 : sqllen));
        break;

    case ECPGt_int: /* integer */
        memcpy(&amp;intval, sqldata, sqllen);
        snprintf(var_buf, sizeof(var_buf), "%d", intval);
        break;

    ...
}
</programlisting>
    </para>
   </sect3>

   <sect3 id="ecpg-sqlda-input">
    <title>Passing Query Parameters Using an SQLDA</title>

    <procedure>
     <para>
      The general steps to use an SQLDA to pass input
      parameters to a prepared query are:
     </para>
     <step><simpara>Create a prepared query (prepared statement)</simpara></step>
     <step><simpara>Declare an sqlda_t structure as an input SQLDA.</simpara></step>
     <step><simpara>Allocate memory area (as sqlda_t structure) for the input SQLDA.</simpara></step>
     <step><simpara>Set (copy) input values in the allocated memory.</simpara></step>
     <step><simpara>Open a cursor with specifying the input SQLDA.</simpara></step>
    </procedure>

    <para>
     Here is an example.
    </para>

    <para>
     First, create a prepared statement.
<programlisting>
EXEC SQL BEGIN DECLARE SECTION;
char query[1024] = "SELECT d.oid, * FROM pg_database d, pg_stat_database s WHERE d.oid = s.datid AND (d.datname = ? OR d.oid = ?)";
EXEC SQL END DECLARE SECTION;

EXEC SQL PREPARE stmt1 FROM :query;
</programlisting>
    </para>

    <para>
     Next, allocate memory for an SQLDA, and set the number of input
     parameters in <structfield>sqln</structfield>, a member variable of
     the <type>sqlda_t</type> structure.  When two or more input
     parameters are required for the prepared query, the application
     has to allocate additional memory space which is calculated by
     (nr. of params - 1) * sizeof(sqlvar_t).  The example shown here
     allocates memory space for two input parameters.
<programlisting>
sqlda_t *sqlda2;

sqlda2 = (sqlda_t *) malloc(sizeof(sqlda_t) + sizeof(sqlvar_t));
memset(sqlda2, 0, sizeof(sqlda_t) + sizeof(sqlvar_t));

sqlda2->sqln = 2; /* number of input variables */
</programlisting>
    </para>

    <para>
     After memory allocation, store the parameter values into the
     <literal>sqlvar[]</literal> array.  (This is same array used for
     retrieving column values when the SQLDA is receiving a result
     set.)  In this example, the input parameters
     are <literal>"postgres"</literal>, having a string