Allocates space for a SQL descriptor area (SQLDA).
ALLOCATE DESCRIPTOR descriptor-name
… [ WITH MAX { integer | host-variable } ]
string
For more information, see Chapter 2, “SQL Language Elements” in Reference: Building Blocks, Tables, and Procedures.
This 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:\\IQ-15_2\\sample.db");
EXEC SQL ALLOCATE DESCRIPTOR sqlda1 WITH MAX 25;
EXEC SQL PREPARE :stmt FROM
'select * from Employees';
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;
}
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;
}
You must declare the following in your C code prior to using this statement:
struct sqlda * descriptor_name
The WITH MAX clause lets you specify the number of variables within the descriptor area. The default size is 1.
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.
DEALLOCATE DESCRIPTOR statement [ESQL]
”The SQL descriptor area (SQLDA)”in SQL Anywhere Server – Programming
