Saving Values in a System-Descriptor Area

If you do not know the number of return values to be supplied at runtime or their data types, you can associate output values with a system-descriptor area. A system-descriptor area describes the data type and memory location of one or more values.

A system-descriptor area conforms to the X/Open standards.

To specify a system-descriptor area as the location of output values, use the INTO SQL DESCRIPTOR clause of the EXECUTE statement. Each time that the EXECUTE statement is run, the values that the system-descriptor area describes are stored in the system-descriptor area.

The following example shows how to use the system-descriptor area to execute prepared statements in : 
EXEC SQL allocate descriptor 'desc1';
...
sprintf(sel_stmt, "%s %s %s", 
   "select fname, lname from customer",
   "where customer_num =",
   cust_num);
EXEC SQL prepare sel1 from :sel_stmt;
EXEC SQL execute sel1 into sql descriptor 'desc1';

The COUNT field corresponds to the number of values that the prepared statement returns. The value of COUNT must be less than or equal to the value of the occurrences that were specified when the system-descriptor area was allocated with the ALLOCATE DESCRIPTOR statement.

You can obtain the value of a field with the GET DESCRIPTOR statement and set the value with the SET DESCRIPTOR statement.

For more information, refer to the discussion of the system-descriptor area in the HCL OneDB™ ESQL/C Programmer's Manual.