Question

I’m writing my first procedure and ge an error. I’ve reduced the error to the delete line but unsure why. Can somebody spot the issue here? Is it the variable?

DROP PROCEDURE IF EXISTS MPT_PROC;
DELIMITER $$
CREATE PROCEDURE MPT_PROC
MODIFIES SQL DATA
BEGIN

    #-- DECLARE statements

    DECLARE v_user_id       INT DEFAULT 0;

    DECLARE no_more_rows    BOOLEAN;
    DECLARE v_loop_cntr     INT DEFAULT 0;
    DECLARE v_num_rows      INT DEFAULT 0;

    DECLARE c_userfiles CURSOR 
    FOR
        SELECT distinct f.user_id
        FROM MPT_STG_FILEUPLOAD f
        WHERE f.status = 'A';  #-- Accepted

        DECLARE CONTINUE HANDLER FOR NOT FOUND
        SET no_more_rows = TRUE;

        OPEN c_userfiles;

        #-- Loop through each user_id found as pending
        the_loop: LOOP

            FETCH c_userfiles INTO v_user_id;

            #-- Break out of the loop if
            #-- 1) there were no records, or
            #-- 2) we've processed them all.
            IF no_more_rows THEN
                CLOSE c_userfiles;
                LEAVE the_loop;
            END IF;

            DELETE FROM MPT_STG_FILEUPLOAD s
            WHERE s.user_id = v_user_id;

            COMMIT;  #--Commiting the changes for this user
        END LOOP the_loop;

    END IF;

END
DELIMITER ;

Answer 1

MySQL doesn’t allow you to provide an alias for a table you are deleting from in a DELETE statement.

 DELETE FROM MPT_STG_FILEUPLOAD WHERE user_id = v_user_id;

And lose the pound signs as comment delimiters. The double dash are the standard for marking the beginning of a comment. It looks like you have an unmatched END IF towards the end of your procedure.

DROP PROCEDURE IF EXISTS MPT_PROC;
DELIMITER $$
CREATE PROCEDURE MPT_PROC
MODIFIES SQL DATA
BEGIN
  DECLARE v_user_id       INT DEFAULT 0;
  DECLARE no_more_rows    BOOLEAN;
  DECLARE v_loop_cntr     INT DEFAULT 0;
  DECLARE v_num_rows      INT DEFAULT 0;

  DECLARE c_userfiles CURSOR 
  FOR
  SELECT distinct f.user_id
    FROM MPT_STG_FILEUPLOAD f
   WHERE f.status = 'A';  -- Accepted

  DECLARE CONTINUE HANDLER FOR NOT FOUND
    SET no_more_rows = TRUE;

  OPEN c_userfiles;

  -- Loop through each user_id found as pending
  the_loop: LOOP

    FETCH c_userfiles INTO v_user_id;

    -- Break out of the loop if
    -- 1) there were no records, or
    -- 2) we've processed them all.
    IF no_more_rows THEN
      CLOSE c_userfiles;
      LEAVE the_loop;
    END IF;

    DELETE FROM MPT_STG_FILEUPLOAD s
     WHERE s.user_id = v_user_id;

    COMMIT;  --Commiting the changes for this user
  END LOOP the_loop;

END$$
DELIMITER ;

---

If user_id is not the primary key on that MPT_STG_FILEUPLOAD table, your procedure could be deleting rows that are NOT marked as “Accepted”. What if a user_id has two rows in that table, and one of the rows is marked as accepted, and the other is not. Did you want to delete both rows?

It looks like you’ve got two variables declared that aren’t being referenced anywhere, v_loop_cntr and v_num_rows, I’d recommend you comment them out if they aren’t needed.

This entire procedure could be done more efficiently in a single SQL statement.