PLSQL觸發 - 基於選擇查詢

Question

更新記錄我有三個表：

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) 

我想有一個觸發器，它在HouseMode表更新開關之後從HouseRoomDevices表更新交換機。

我的觸發器：

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，當我嘗試更新的記錄：

UPDATE HouseMode 
SET switch = 1 
WHERE mode_id = 1; 

它從HouseRoomDevices表更新中的所有記錄。

Answer 1

您的更新語句錯誤，因爲您的WHERE條件始終爲真。使用這一個：

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