我在创建一个触发器时遇到了一些麻烦,该触发器将获得一个人的当前积分,请检查他将获得什么奖励,然后更新他的奖励头衔。所以这是场景:
PersonTable
| Person (PK) | RewardTitle (FK) | Score|
| A | Beginner | 0 |
| B | MidRange | 17 |
| C | Professional | 32 |
RewardTable
| RewardTitle (PK) | BottomScore | UpperScore| Reward |
| Beginner | 0 | 9 | Free food |
| MidRange | 10 | 19 | Free games |
| Professional | 20 | 100 | Unlimited time|
情况是,我想更新人A,以便他现在有11分,然后找出他的新积分属于哪个奖励头衔,并相应地更改他的奖励头衔,所以由于他有11分,他的奖励头衔现在将是中档。
我试图创建一个触发器,试图找到他所属的 RewardTitle,然后相应地更新此值,但我不断收到一条错误消息:
Person is mutating, trigger/function may not see it
我理解这个问题,但我想不出任何其他方法来达到结果。我试过使用
pragma autonomous_transaction;
但它仍然没有奏效,这是我在下面的尝试:
UPDATE PersonTable
SET Score = 11
WHERE Person = 'A';
DELIMITER //
CREATE OR REPLACE TRIGGER person_upd_trigger
AFTER UPDATE ON PersonTable
FOR EACH ROW
DECLARE
temp_variable VARCHAR(120);
BEGIN
SELECT r.RewardTitle INTO temp_variable
FROM PersonTable p, RewardTable r
WHERE :NEW.Person = p.Person
AND p.Score BETWEEN r.BottomScore AND r.UpperScore;
UPDATE PersonTable
SET RewardTitle = temp_variable
WHERE :NEW.Person = Person;
END;
我将非常感谢我能得到的所有帮助,我对Oracle SQL很陌生。谢谢
您无法在 BEFORE 触发器中更新已经更新的同一表(如果允许会导致无限循环)。相反,您需要将触发器重写为:
为了使其正常工作,您应该将触发器定义更改为BEFORE
CREATE OR REPLACE TRIGGER person_upd_trigger
BEFORE UPDATE ON PersonTable -- declare it as BEFORE
FOR EACH ROW
DECLARE
temp_variable VARCHAR(120);
BEGIN
SELECT r.RewardTitle INTO temp_variable
FROM RewardTable r
WHERE :NEW.Score BETWEEN r.BottomScore AND r.UpperScore;
-- here you are setting the new value, no need for an update.
:NEW.RewardTitle := temp_variable;
END;