HP 3000 Manuals HP 3000 Manuals
Dynamic Operations
Dynamic operations offer a way to execute SQL commands that cannot be
completely defined until run time. You accept part or all of an SQL
command that can be dynamically preprocessed from the user, then use one
of the following techniques to preprocess and execute the command:
* You can use the PREPARE command to preprocess a command, then
execute it later during the same transaction using the EXECUTE
command. The PREPARE and EXECUTE commands must be in the same
program or subprogram.
* You can use the EXECUTE IMMEDIATE command to preprocess and
execute an SQL command in one step.
The data manipulation commands you can dynamically preprocess from an
ALLBASE/SQL COBOL program are: DELETE, INSERT, and UPDATE. Refer to the
ALLBASE/SQL Reference Manual for a list of other commands you can
dynamically preprocess.
In the following example, an SQL command entered by the program user is
handled by using the PREPARE and EXECUTE commands. The command to
be dynamically preprocessed is stored in a host variable named
DYNAMICCOMMAND, declared to be 1024 bytes long, the maximum length of a
dynamically preprocessed SQL command.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
01 DYNAMICCOMMAND PIC X(1024).
EXEC SQL END DECLARE SECTION END-EXEC.
.
.
.
PROCEDURE DIVISION
The program accepts an SQL command from the
user and moves it into DYNAMICCOMMAND for
preprocessing.
EXEC SQL PREPARE DYNAMCOMMAND FROM :DYNAMICCOMMAND END-EXEC.
Later during the same transaction, the prepared
command is executed as follows:
EXEC SQL EXECUTE DYNAMCOMMAND END-EXEC.
Dynamic preprocessing from a COBOL program is addressed in Chapter 10.