使用更新觸發器僅在歷史表中插入修改后的值

Question

我想使用觸發器，所以當我更新MyTable上的一列時，我會在歷史表中插入MyTable的舊值

CREATE TRIGGER historytrigger
   ON MyTable 
   BEFORE UPDATE
as
BEGIN  
if UPDATING(`Unit`) 
INSERT INTO `historytable`(`id_forecast`, `Unit`) VALUES (old.`ID`, old.`Unit`);
ELSEIF UPDATING(`Project_Country`) 
INSERT INTO `historytable`(`id_forecast`, `Project_Country`) VALUES (old.`ID`, old.`Project_Country`);
.
.
.
.
END

這有語法錯誤。

Answer 1

我是怎么解決這個問題的

begin 
IF OLD.`column`!= NEW.`column` THEN
INSERT INTO `historytable` (`id_forecast`, `Unit`) VALUES (old.`ID`, old.`column`);
ELSEIF OLD.`column1`!= NEW.`column1` THEN
INSERT INTO `historytable` (`id_forecast`, `Project_Country`) VALUES (old.`ID`, old.`column1`);
ELSEIF OLD.`column2`!= NEW.`column2` THEN
INSERT INTO `historytable` (`id_forecast`, `Project_Country`) VALUES (old.`ID`, old.`column2`);
ELSEIF OLD.`column3`!= NEW.`column3` THEN
INSERT INTO `edited_forecasts` (`id_forecast`, `Project_Country`) VALUES (old.`ID`, old.`column3`);
END IF
end