ASA SQL Reference
  SQL Statements

ALLOCATE DESCRIPTOR statement [ESQL]

Description 

Use this statement to allocate space for a SQL descriptor area (SQLDA).

Syntax 

ALLOCATE DESCRIPTOR descriptor-name
[ WITH MAX { integer | hostvar } ]

descriptor-name : string

Parameters 

WITH MAX clause    Allows you to specify the number of variables within the descriptor area. The default size is one. You must still call fill_sqlda to allocate space for the actual data items before doing a fetch or any statement that accesses the data within a descriptor area.

Usage 

Allocates space for a descriptor area (SQLDA). You must declare the following in your C code prior to using this statement:

struct sqlda * descriptor_name

Permissions 

None.

Side effects 

None.

See also 

DEALLOCATE DESCRIPTOR statement [ESQL]

The SQL descriptor area (SQLDA)

Standards and compatibility 

• SQL/92    Entry-level feature.

• SQL/99    Core feature.

• Sybase    Supported by Open Client/Open Server.

Example 

The following sample program includes an example of ALLOCATE DESCRIPTOR statement usage.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
EXEC SQL INCLUDE SQLCA;
#include <sqldef.h>
EXEC SQL BEGIN DECLARE SECTION;
int         x;
short       type;
int         numcols;
char        string[100];
a_SQL_statement_number  stmt = 0;
EXEC SQL END DECLARE SECTION;
int main(int argc, char * argv[]){
   struct sqlda *      sqlda1;
   if( !db_init( &sqlca ) ) {
      return 1;
   }
   db_string_connect( &sqlca,
   "UID=DBA;PWD=SQL;DBF=d:\\DB Files\\sample.db");
   EXEC SQL ALLOCATE DESCRIPTOR sqlda1 WITH MAX 25;
   EXEC SQL PREPARE :stmt FROM
      'SELECT * FROM employee';
   EXEC SQL DECLARE curs CURSOR FOR :stmt;
   EXEC SQL OPEN curs;
   EXEC SQL DESCRIBE :stmt into sqlda1;
   EXEC SQL GET DESCRIPTOR sqlda1 :numcols=COUNT;
   // how many columns?
   if( numcols > 25 ) {
      // reallocate if necessary
      EXEC SQL DEALLOCATE DESCRIPTOR sqlda1;
      EXEC SQL ALLOCATE DESCRIPTOR sqlda1
         WITH MAX :numcols;
      EXEC SQL DESCRIBE :stmt into sqlda1;
   }
   type = DT_STRING; // change the type to string
   EXEC SQL SET DESCRIPTOR sqlda1 VALUE 2 TYPE = :type;
   fill_sqlda( sqlda1 );
   // allocate space for the variables
   EXEC SQL FETCH ABSOLUTE 1 curs
      USING DESCRIPTOR sqlda1;
   EXEC SQL GET DESCRIPTOR sqlda1
      VALUE 2 :string = DATA;
   printf("name = %s", string );
   EXEC SQL DEALLOCATE DESCRIPTOR sqlda1;
   EXEC SQL CLOSE curs;
   EXEC SQL DROP STATEMENT :stmt;
   db_string_disconnect( &sqlca, "" );
   db_fini( &sqlca );
   return 0;
}