来自触发器MySQL的结果集

这是我第一次使用触发器，我有点麻烦。 我正在创建一个通知系统，当创建一个新通知时，它将向notify表中添加一行。添加的内容取决于通知类型

到目前为止，我已经尝试：

DELIMITER $$
DROP TRIGGER IF EXISTS generate_notify $$
CREATE TRIGGER generate_notify
AFTER INSERT 
ON notifications
FOR EACH ROW
BEGIN

SELECT @group := notify_group FROM notification_types WHERE type=NEW.type;
IF (@group <> 1) THEN
INSERT INTO notify (user_id, notification_id) VALUES (NEW.user_reference, NEW.id);
ELSE

INSERT INTO notify (user_id, notification_id) VALUES(
    SELECT ID, NEW.id FROM user_customer WHERE clientID=NEW.user_reference
);
END IF;
END; $$
DELIMITER ;

我四处搜索，然后将其更改为：

DELIMITER $$
DROP TRIGGER IF EXISTS generate_notify $$
CREATE TRIGGER generate_notify
AFTER INSERT 
ON notifications
FOR EACH ROW
BEGIN
DECLARE insert_user_id INT(11);
SELECT @group := notify_group FROM notification_types WHERE type=NEW.type;
IF (@group <> 1) THEN
INSERT INTO notify (user_id, notification_id) VALUES (NEW.user_reference, NEW.id);
ELSE
SELECT ID INTO insert_user_id FROM user_customer WHERE clientID=NEW.user_reference;
INSERT INTO notify (user_id, notification_id) VALUES(insert_user_id, NEW.id);
END IF;
END; $$
DELIMITER ;

我还尝试将上述两种方法混合在一起，得到的结果要么是无法返回结果集，要么是select查询出现语法错误

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另外，我假设NEW关键字是为触发器预定义的？

您的第一次尝试实际上是正确的，但是您没有将SELECT的结果写入变量。无法从触发器返回结果集

DELIMITER $$
DROP TRIGGER IF EXISTS generate_notify $$
CREATE TRIGGER generate_notify
AFTER INSERT 
ON notifications
FOR EACH ROW
BEGIN

DECLARE v_group INT;

SELECT notify_group INTO v_group FROM notification_types WHERE type=NEW.type;
IF (v_group <> 1) THEN
    INSERT INTO notify (user_id, notification_id) VALUES (NEW.user_reference, NEW.id);
ELSE
    INSERT INTO notify (user_id, notification_id) VALUES(
    SELECT ID, NEW.id FROM user_customer WHERE clientID=NEW.user_reference
);
END IF;
END $$
DELIMITER ;

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谢谢你的帮助，@fancyPants，它起了很大的作用！：