firebird/examples/api/api5.c

/*
 *    Program type:  API Interface
 *
 *    Description:
 *        This program demonstrates the reallocation of SQLDA
 *        and the 'isc_dsql_describe' statement.  After a query
 *        is examined with 'isc_dsql_describe', an SQLDA of correct
 *        size is reallocated, and some information is printed about
 *        the query:  its type (select, non-select), the number
 *        of columns, etc.
 * The contents of this file are subject to the Interbase Public
 * License Version 1.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy
 * of the License at http://www.Inprise.com/IPL.html
 *
 * Software distributed under the License is distributed on an
 * "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express
 * or implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code was created by Inprise Corporation
 * and its predecessors. Portions created by Inprise Corporation are
 * Copyright (C) Inprise Corporation.
 *
 * All Rights Reserved.
 * Contributor(s): ______________________________________.
 */

#include <stdlib.h>
#include <string.h>
#include <ibase.h>
#include <stdio.h>
#include "example.h"

char *sel_str =
     "SELECT department, mngr_no, location, head_dept \
      FROM department WHERE head_dept in ('100', '900', '600')";

isc_db_handle    DB = 0;                       /* database handle */
isc_tr_handle    trans = 0;                    /* transaction handle */
ISC_STATUS_ARRAY status;                       /* status vector */


int main (int argc, char** argv)
{
    int                num_cols, i;
    isc_stmt_handle    stmt = NULL;
    XSQLDA             *sqlda;
    char               empdb[128];

    if (argc > 1)
         strcpy(empdb, argv[1]);
    else
         strcpy(empdb, "employee.fdb");

    if (isc_attach_database(status, 0, empdb, &DB, 0, NULL))
    {
        ERREXIT(status, 1)
    }

    /* Allocate SQLDA of an arbitrary size. */
    sqlda = (XSQLDA *) malloc(XSQLDA_LENGTH(3));
    sqlda->sqln = 3;
    sqlda->version = 1;

    if (isc_start_transaction(status, &trans, 1, &DB, 0, NULL))
    {
        ERREXIT(status, 1)
    }

    /* Allocate a statement. */
    if (isc_dsql_allocate_statement(status, &DB, &stmt))
    {
        ERREXIT(status, 1)
    }

    /* Prepare the statement. */
    if (isc_dsql_prepare(status, &trans, &stmt, 0, sel_str, 1, sqlda))
    {
        ERREXIT(status, 1)
    }

    /* Describe the statement. */
    if (isc_dsql_describe(status, &stmt, 1, sqlda))
    {
        ERREXIT(status, 1)
    }
    
    /* This is a select statement, print more information about it. */

    printf("Query Type:  SELECT\n\n");

    num_cols = sqlda->sqld;

    printf("Number of columns selected:  %d\n", num_cols);

    /* Reallocate SQLDA if necessary. */
    if (sqlda->sqln < sqlda->sqld)
    {
        sqlda = (XSQLDA *) malloc(XSQLDA_LENGTH(num_cols));
        sqlda->sqln = num_cols;
        sqlda->version = 1;
    
        /* Re-describe the statement. */
        if (isc_dsql_describe(status, &stmt, 1, sqlda))
        {
            ERREXIT(status, 1)
        }

        num_cols = sqlda->sqld;
    }

    /* List column names, types, and lengths. */
    for (i = 0; i < num_cols; i++)
    {
        printf("\nColumn name:    %s\n", sqlda->sqlvar[i].sqlname);
        printf("Column type:    %d\n", sqlda->sqlvar[i].sqltype);
        printf("Column length:  %d\n", sqlda->sqlvar[i].sqllen);
    }


    if (isc_dsql_free_statement(status, &stmt, DSQL_drop))
    {
        ERREXIT(status, 1)
    }

    if (isc_commit_transaction(status, &trans))
    {
        ERREXIT(status, 1)
    }

    if (isc_detach_database(status, &DB))
    {
        ERREXIT (status, 1)
    }

    free(sqlda);

    return 0;
}