PLSQL 触发器 - 根据 select 查询更新记录

Question

我有三个table：

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，它在更新 HouseMode table 中的开关后从 HouseRoomDevices table 更新开关。

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;

它更新来自 HouseRoomDevices table 的所有记录。

Answer 1

你的更新语句是错误的，因为你的 WHERE 条件总是为真。使用这个：

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

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