如何在 UPDATE 后在 Postgresql 中创建触发器

Question

我有桌子Room Details ：

和Log Room Status ：

我想创造一个当触发room details表我更改了status栏，然后在log room status表中的status前和状态会自动改变后列。 例如，当Room Details的状态为Vacant Dirty并且我将其更改为Vacant Clean ，则 Before status 列中的日志房间状态将填充Vacant Dirty并且 after 状态将填充Vacant Clean

这是我的代码：

CREATE OR REPLACE FUNCTION public.log_rs_history()
  RETURNS trigger AS
$BODY$DECLARE

BEGIN
IF status = 'UPDATE' THEN
UPDATE log_room_status set status_before=old.status_before, status_after=new.status_after where id_room=id_room and room_number=room_number;
      END IF;
  RETURN new;
END$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

  CREATE TRIGGER log_history
  AFTER UPDATE
  ON public.room_details
  FOR EACH ROW
  EXECUTE PROCEDURE public.product_hs_history();    

Answer 1

你很接近。 我想你的意思是这样做：

CREATE OR REPLACE FUNCTION public.log_rs_history()
  RETURNS trigger AS
$BODY$
DECLARE
BEGIN
IF TG_OP = 'UPDATE' THEN
  UPDATE log_room_status
     SET status_before=old.status,
         status_after=new.status
   WHERE id_room=new.id_room
     AND room_number=new.room_number;
  END IF;
  RETURN new;
END
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;

CREATE TRIGGER log_history
  AFTER UPDATE
  ON public.room_details
  FOR EACH ROW
  EXECUTE PROCEDURE public.log_rs_history();