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 type,
     and <literal>1</literal>, having an integer type.
<programlisting>
sqlda2->sqlvar[0].sqltype = ECPGt_char;
sqlda2->sqlvar[0].sqldata = "postgres";
sqlda2->sqlvar[0].sqllen  = 8;

int intval = 1;
sqlda2->sqlvar[1].sqltype = ECPGt_int;
sqlda2->sqlvar[1].sqldata = (char *) &amp;intval;
sqlda2->sqlvar[1].sqllen  = sizeof(intval);
</programlisting>
    </para>

    <para>
     By opening a cursor and specifying the SQLDA that was set up
     beforehand, the input parameters are passed to the prepared
     statement.
<programlisting>
EXEC SQL OPEN cur1 USING DESCRIPTOR sqlda2;
</programlisting>
    </para>

    <para>
     Finally, after using input SQLDAs, the allocated memory space
     must be freed explicitly, unlike SQLDAs used for receiving query
     results.
<programlisting>
free(sqlda2);
</programlisting>
    </para>
   </sect3>

   <sect3 id="ecpg-sqlda-example">
    <title>A Sample Application Using SQLDA</title>

    <para>
     Here is an example program, which describes how to fetch access
     statistics of the databases, specified by the input parameters,
     from the system catalogs.
    </para>

    <para>
     This application joins two system tables, pg_database and
     pg_stat_database on the database OID, and also fetches and shows
     the database statistics which are retrieved by two input
     parameters (a database <literal>postgres</literal>, and OID <literal>1</literal>).
    </para>

    <para>
     First, declare an SQLDA for input and an SQLDA for output.
<programlisting>
EXEC SQL include sqlda.h;

sqlda_t *sqlda1; /* an output descriptor */
sqlda_t *sqlda2; /* an input descriptor  */
</programlisting>
    </para>

    <para>
     Next, connect to the database, prepare a statement, and declare a
     cursor for the prepared statement.
<programlisting>
int
main(void)
{
    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 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 :query;
    EXEC SQL DECLARE cur1 CURSOR FOR stmt1;
</programlisting>
    </para>

    <para>
     Next, put some values in the input SQLDA for the input
     parameters.  Allocate memory for the input SQLDA, and set the
     number of input parameters to <literal>sqln</literal>.  Store
     type, value, and value length into <literal>sqltype</literal>,
     <literal>sqldata</literal>, and <literal>sqllen</literal> in the
     <literal>sqlvar</literal> structure.

<programlisting>
    /* Create SQLDA structure for input parameters. */
    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 */

    sqlda2->sqlvar[0].sqltype = ECPGt_char;
    sqlda2->sqlvar[0].sqldata