There are two types of SQL descriptor areas.
One is defined with the ALLOCATE DESCRIPTOR statement. The other is defined
using the SQLDA structure. In this section, only the SQLDA form is discussed.
The following statements can use an SQLDA:
- EXECUTE…USING DESCRIPTOR descriptor-name
- FETCH…USING DESCRIPTOR descriptor-name
- OPEN…USING DESCRIPTOR descriptor-name
- CALL…USING DESCRIPTOR descriptor-name
- DESCRIBE statement-name INTO descriptor-name
- DESCRIBE INPUT statement-name INTO descriptor-name
- DESCRIBE TABLE host-variable INTO descriptor-name
- PREPARE statement-name INTO descriptor-name
Unlike the SQLCA, there can be more than one SQLDA in a program, and an SQLDA can have any valid name. An SQLDA can be coded in a PL/I program either program directly or by using the SQL INCLUDE statement. Using the SQL INCLUDE statement requests the inclusion of a standard SQLDA declaration:
EXEC SQL INCLUDE SQLDA ;
The included PL/I source statements for the SQLDA are:
DCL 1 SQLDA BASED(SQLDAPTR),
2 SQLDAID CHAR(8),
2 SQLDABC FIXED(31) BINARY,
2 SQLN FIXED(15) BINARY,
2 SQLD FIXED(15) BINARY,
2 SQLVAR(99),
3 SQLTYPE FIXED(15) BINARY,
3 SQLLEN FIXED(15) BINARY,
3 SQLRES CHAR(12),
3 SQLDATA PTR,
3 SQLIND PTR,
3 SQLNAME CHAR(30) VAR;
DCL SQLDAPTR PTR;
Dynamic SQL is an advanced programming technique. With dynamic SQL, your program can develop and then run SQL statements while the program is running. A SELECT statement with a variable SELECT list (that is, a list of the data to be returned as part of the query) that runs dynamically requires an SQL descriptor area (SQLDA). This is because you cannot know in advance how many or what type of variables to allocate in order to receive the results of the SELECT.