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create table mytable(
watch int,
not_watch int,
safeguard int );
CREATE TRIGGER updtrigger BEFORE UPDATE ON mytable
FOR EACH ROW
BEGIN
IF NEW.watch <> OLD.watch THEN
SET NEW.safeguard = new.watch;
END IF;
END
insert into mytable values (25,20,0);
update mytable set watch = 50;
Rows matched: 1 Changed: 1 Warnings: 0
select * from mytable;
| watch | not_watch | safeguard |
|---|---|---|
| 50 | 20 | 50 |
update mytable set watch = 75;
Rows matched: 1 Changed: 1 Warnings: 0
select * from mytable;
| watch | not_watch | safeguard |
|---|---|---|
| 75 | 20 | 75 |
update mytable set not_watch = 100;
Rows matched: 1 Changed: 1 Warnings: 0
select * from mytable;
| watch | not_watch | safeguard |
|---|---|---|
| 75 | 100 | 75 |