Why does using the IF-ENDIF block in this DB2 function cause - db2

Question

Why does using the IF statement in this function result in error 42601 [SQL0104], as shown below..? This is DB2-400 for i v7r3m0.
SQL Error [42601]: [SQL0104] Token <END-OF-STATEMENT> was not valid. Valid tokens: ;.
The code example I provide below executes without error until the IF statement is uncommented. I've tried moving the semicolons around and even removing them, but then the errors get worse and begin pointing to later statements being invalid.
I've checked the IBM documentation for IF on v7r3, and my syntax seems to be correct. Other code examples follow the same syntax as that and mine. I'm stumped.
CREATE OR REPLACE FUNCTION F_CERT.CERT_UPC_COMMON_DESC (UPC NUMERIC(14))
RETURNS INTEGER
LANGUAGE SQL
GLOBAL DETERMINISTIC
NO EXTERNAL ACTION
NOT FENCED
ALLOW PARALLEL
BEGIN
DECLARE RETVAL INTEGER DEFAULT 0 ;
DECLARE UPC_COUNT INTEGER DEFAULT 0 ;
DECLARE UPC_LIST CURSOR FOR
SELECT COUNT(*)
FROM F_CERTOB.BEERXT
WHERE BXUPCR=UPC
;
OPEN UPC_LIST ;
FETCH UPC_LIST INTO UPC_COUNT ;
CLOSE UPC_LIST ;
-- IF UPC_COUNT > 0 THEN
-- -- OTHER
-- -- COMMANDS
SET RETVAL = UPC_COUNT ;
-- END IF ;
RETURN RETVAL ;
END ;
SELECT F_CERT.CERT_UPC_COMMON_DESC (793936791660) AS C FROM SYSIBM.SYSDUMMY1 ;
EDIT:
Here is a second example; a trimmed-down version. As with the code above, everything is fine until the IF statements are uncommented:
CREATE OR REPLACE FUNCTION F_CERT.CERT_UPC_COMMON_DESC (UPC NUMERIC(14))
RETURNS INTEGER
LANGUAGE SQL
BEGIN
DECLARE RETVAL INTEGER DEFAULT 0 ;
-- IF 1=1 THEN
SET RETVAL = 1 ;
-- ELSE
SET RETVAL = 100 ;
-- END IF ;
RETURN RETVAL ;
END ;
SELECT F_CERT.CERT_UPC_COMMON_DESC (12345) AS C FROM SYSIBM.SYSDUMMY1 ;

Answer 1

I've continued searching since my OP, and I finally found the exact solution
here.
The issue is the statement delimiter. A conflict arises when the function contains flow-control and similarly structured statements that span multiple lines. In my code example, the compiler stops at END IF; and thinks that's all there is, instead of continuing to the END; of the function.
My SQL client is DBeaver 5.2.5, and it does have some functionality to run statements & scripts in different ways. This article gave me the idea to try running my CREATE script with the different actions of DBeaver, and I discovered I could make it work if I highlighted the whole script from CREATE to END but not including the trailing semicolon. Then I used Execute Statement {Ctrl+Enter} instead of the usual Execute Sctipt {Alt+X}. And it finally worked..!! But that seemed "kludgy" so I continued searching for a solution.
Then I found the imperfect, but perfectly acceptable solution in the main article mentioned above. I followed the directions to change the settings in my DBeaver client, and edited my code as shown below (notice the # characters). And then it finally worked..!! I could run the whole script, including the SELECT statement, and was able to do so with the usual Execute Statement {Alt+X} keystroke that I've become accustomed to.
CREATE OR REPLACE FUNCTION F_CERT.CERT_UPC_COMMON_DESC (UPC NUMERIC(14))
RETURNS INTEGER
LANGUAGE SQL
BEGIN
DECLARE RETVAL INTEGER DEFAULT 0;
IF 1=0 THEN
SET RETVAL = 1;
ELSE
SET RETVAL = 100;
END IF;
RETURN RETVAL;
END #
SELECT F_CERT.CERT_UPC_COMMON_DESC (793936791660) AS C FROM SYSIBM.SYSDUMMY1 #