PLSQL 触发器 - 基于选择查询更新记录

Question

我有三张桌子：

HouseMode:
mode_id (INT, PK)
switch (CHAR 1BYTE)

ModeDevices:
modedevice_id (INT, PK)
house_mode (INT, FK)
houseroomdevice (INT, FK)

HouseRoomDevices:
houseroomdevice_id (INT, PK)
switch (CHAR 1BYTE)

我想要一个触发器，在更新HouseMode 表中的开关后更新来自HouseRoomDevices 表的开关。

我的触发器：

CREATE OR REPLACE TRIGGER switch
BEFORE UPDATE
ON HouseMode
FOR EACH ROW
BEGIN
  UPDATE houseroomdevices
  SET switch = :NEW.switch
  WHERE EXISTS(SELECT houseroomdevice_id FROM houseroomdevices INNER JOIN modedevices ON houseroomdevice = houseroomdevice_id WHERE house_mode = :NEW.mode_id);
END;

但是当我尝试更新记录时：

UPDATE HouseMode
SET switch = 1
WHERE mode_id = 1;

它会更新 HouseRoomDevices 表中的所有记录。

Answer 1

您的更新语句是错误的，因为您的 WHERE 条件始终为真。使用这个：

UPDATE houseroomdevices
SET switch = :NEW.switch
WHERE houseroomdevice_id IN  (SELECT houseroomdevice FROM modedevices WHERE house_mode = :NEW.mode_id);