如何使用我的學生表阻止未來的日期？

Question

-- Create a trigger that will prevent an update to a student table if EnrolledDate is in the future 
 

 
USE College ; 
 

 
DROP TRIGGER IF EXISTS Student_Before_Update; 
 

 
DELIMITER $$ 
 

 
     CREATE TRIGGER Student_Before_Update 
 
     BEFORE UPDATE ON Student 
 
     FOR EACH ROW 
 
     
 
     BEGIN 
 
     
 
\t IF NEW.EnrolledDate > '2016-10-18' THEN 
 
\t \t \t \t SIGNAL SQLSTATE VALUE '45000' 
 
\t \t \t \t SET MESSAGE_TEXT= 'Enrolled date may not be in the future'; 
 
\t \t END IF; 
 

 
     END $$ 
 

 
DELIMITER ; 
 

 
UPDATE Student 
 
SET EnrolledDate= DATE(now()) 
 
WHERE ID= 1; 
 

 
UPDATE Student 
 
SET EnrolledDate= DATE_ADD(now(),INTERVAL 1 DAY) 
 
WHERE ID=1;

大家好，

我的工作創造一個BEFORE UPDATE觸發器如果我更新學生的EnrolledDate與將來的日期，應顯示錯誤 消息。例如，Student表中最後插入的EnrolledDate爲'2016-04-17'，因此該日期之後的任何其他記錄都應標記錯誤消息，指出「註冊日期可能不在將來」。我幾個小時以來一直在努力研究這個問題，但我仍然無法得到。有人可以幫幫我嗎？這是我的代碼到目前爲止。

Answer 1

試試這個：

-- Create a trigger that will prevent an update to a student table if EnrolledDate is in the future 

USE College ; 

DROP TRIGGER IF EXISTS Student_Before_Update; 

DELIMITER $$ 

CREATE TRIGGER Student_Before_Update 
BEFORE UPDATE ON Student 
FOR EACH ROW 

BEGIN 

    IF DATE_FORMAT(NEW.EnrolledDate,'%Y-%m-%d') > DATE_FORMAT(NOW(),'%Y-%m-%d') THEN 
     SIGNAL SQLSTATE VALUE '45000' 
     SET MESSAGE_TEXT= 'Enrolled date may not be in the future'; 
    END IF; 

END $$ 

DELIMITER ; 

UPDATE Student 
SET EnrolledDate= DATE(now()) 
WHERE ID= 1; 

UPDATE Student 
SET EnrolledDate= DATE_ADD(now(),INTERVAL 1 DAY) 
WHERE ID=1;