Optional Arguments/Cursors in DML Programs

Question

I am trying to write a DML program which needs to have optional arguments. I am having issues when executing a SQL based on whether the argument is supplied or not.
My program is defined as below:
VARIABLE v_ARG TEXT
if ARG(1) ne ''
then do
SQL DECLARE a_cur CURSOR FOR select ARG(1) from dual
doend
else do
SQL DECLARE a_cur CURSOR FOR select '1275' from dual
doend
SQL OPEN a_cur
SQL IMPORT a_cur INTO :v_ARG
SQL CLOSE a_cur
SQL CLEANUP
show joinchars('Value set is ', v_ARG)
The output of the program without and with arguement is as follows:
->call TEST_PRG
Value set is 1275
->call TEST_PRG(111)
ORA-35572: (SQLOUT09) SQL cursor 'A_CUR' is not open.
->call TEST_PRG('111')
ORA-35572: (SQLOUT09) SQL cursor 'A_CUR' is not open.
I have two questions. How to solve the above problem with cursors being not open? Also, Is there a preferred way to deal with optional arguments or the above approach is fine?
Any help is greatly appreciated.
Thanks
Swapan.

Answer 1

First, the issue was not multiple SQL DECLARE commands. Sorry.
The program is that the MD engine wants any program that includes SQL DECLARE (and maybe other SQL commands) to be compiled before it is run. So, if you need to generate the SELECT dynamically you should generate a program and then run that program. Here's an example.
The TEST program is a driver.
DEFINE TEST PROGRAM
PROGRAM
VRB _result text
" Call the program that generates the program with SQL commands. This program
" creates a function named SELECTPRG
call GENERATE_SELECT_PROGRAM(ARG(1))
" Assign the result of the _SELECT_PRG function into _RESULT
_result = _select_prg
" Show the result.
show _result
Here's the GENERATE_SELECT_PROGRAM:
DEFINE GENERATE_SELECT_PROGRAM PROGRAM
PROGRAM
vrb _select text
vrb _prg    text
vrb _result text
" Check of the program exists. If not, create it.
if exists('_select_prg') eq NO
then define _select_prg program text
" Construct the SQL DECLARE command
if ARG(1) eq ''
THEN select = joinchars('SQL DECLARE acur CURSOR FOR SELECT \'ABCDEFG\' FROM DUAL')
ELSE select = joinchars('SQL DECLARE acur CURSOR FOR SELECT ' , '\'' , ARG(1) , '\'' , ' FROM DUAL')
" Generate text of a program with the SQL commands
_prg = 'vrb _result text'
_prg = joinlines(_prg , _select)
_prg = joinlines(_prg , 'SQL OPEN a_cur')
_prg = joinlines(_prg , 'SQL IMPORT a_cur INTO :_result')
_prg = joinlines(_prg , 'SQL CLOSE a_cur')
_prg = joinlines(_prg , 'SQL CLEANUP')
_prg = joinlines(_prg , 'RETURN _result')
" Assign the program text to the program
consider selectprg
program _prg
END
It produces a program like this:
DEFINE SELECTPRG PROGRAM TEXT
PROGRAM
vrb _result text
SQL DECLARE a_cur CURSOR FOR SELECT 'ABCDEFG' FROM DUAL
SQL OPEN a_cur
SQL IMPORT a_cur INTO :_result
SQL CLOSE a_cur
SQL CLEANUP
RETURN _result
END
So, if I run test I get:
-> test
ABCDEFG
->test 'Hello Swapan, I hope this helps'
Hello Swapan, I hope this helps