Question

mysql> select * from S_TABLE;
+--------+--------------------+
|   S_ID | S_TITLE            |
+--------+--------------------+
|      1 |  Jim               |
|      2 |  George            |
|      3 |  Sam               |
|      4 |  Zoe               |
+--------+--------------------+

mysql> select * from F_TABLE;
+--------+--------+--------------+----------+
| F_ID   |  S_ID  | F_VALUE      | F_TITLE  |
+--------+--------+--------------+----------+
|      1 |      1 | 4.5          | Delta    |
|      2 |      2 | 24.5         | Gamma    |
|      3 |      3 | 44.4         | RHO      |
|      4 |      3 | 5.0          | Beta     |
+--------+--------+--------------+----------+

mysql> select * from Results; // Hence this table is empty
+--------+-------------+
| Fstuff | Sstuff      |
+--------+-------------+
|        |             |
+--------+-------------+

This stored procedure does a frivolous computation

DELIMITER ##
CREATE PROCEDURE zap(IN sss VARCHAR(30))
BEGIN 

INSERT INTO Results (fstuff, Sstuff)
Select 
f.F_VALUE * 0 + 123,
s.S_TITLE
FROM F_TABLE f
JOIN S_TABLE s ON s.S_ID=f.S_ID
WHERE s.S_TITLE LIKE CONCAT('%', sss, '%');

END ##
DELIMITER ;

This stored procedure calls zap

DELIMITER ##
CREATE PROCEDURE crap()
BEGIN
    DECLARE fTit VARCHAR(30);
    DECLARE done INT DEFAULT 0;
    DECLARE cur CURSOR FOR SELECT F_TITLE FROM F_TABLE;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

    OPEN cur;
    read_loop: LOOP

        FETCH cur INTO fTit;

        IF done 
            THEN LEAVE read_loop;
        END IF;

        call Zap(fTit);
        COMMIT;

    END LOOP;
    CLOSE cur;

END ##
DELIMITER ;

Problem: Result table becomes uneffected? I cant figure out why

Answer 1

You read out the names from F_TABLE.F_TITLE (Delta,Gamma…) and look for them in S_TABLE.S_TITLE and there is no match.

The cursor in crap should use the same title column as the zap procedure.

edit:

The cursor cur CURSOR FOR SELECT F_TITLE FROM F_TABLE; will fetch ‘Delta’,’Gamma’ and so on into fTit. Then Zap() is called:
Zap('Delta'), Zap('Gamma') etc.

The Zap procedure will create a match string '%Delta%', '%Gamma%' and so on and look for this in the first table you listed. Since that table contains ‘Jim’, ‘George’ and other names there is no match. The SELECT returns no rows so there is nothing inserted in any of the calls to zap.

If you change the cursor to instead look in S_TABLE you will get rows inserted, but maybe not the ones you want. Please explain more what you expect in the results table.