触发器

数据库/头歌/触发器的创建和使用/1. 触发器的创建和使用.sh

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+USE studentdb
+go
+
+SET NOCOUNT ON 
+go
+--********** create trigger_insert_score  **********--
+--********** Begin **********--
+CREATE TRIGGER trigger_insert_score  
+ON score  
+INSTEAD OF INSERT  
+AS  
+BEGIN  
+    IF EXISTS (SELECT * FROM inserted i WHERE NOT EXISTS (SELECT 1 FROM student s WHERE s.sno = i.sno))  
+    BEGIN  
+        RETURN  
+    END  
+    INSERT INTO score (sno, cno, grade)  
+    SELECT sno, cno, grade FROM inserted  
+END  
+--********** End **********--
+go
+delete from score
+go
+insert into score values('1001','2001','89.5')
+go
+insert into score values('1002','2001','95')
+go
+insert into score values('1011','2001','88')
+go
+select * from score
+go
+
+
+--********** create trigger_delete_student  **********--
+--********** Begin **********--
+CREATE TRIGGER trigger_delete_student  
+ON student  
+INSTEAD OF DELETE  
+AS  
+BEGIN  
+    DELETE FROM score WHERE sno IN (SELECT sno FROM deleted)  
+    DELETE FROM student WHERE sno IN (SELECT sno FROM deleted)  
+END  
+--********** End **********--
+go
+delete from student where sno='1001'
+go
+select * from student
+go
+
+--********** create trigger_protect_grade **********--
+--********** Begin **********--
+CREATE TRIGGER trigger_protect_grade  
+ON score  
+FOR UPDATE  
+AS  
+BEGIN  
+    IF UPDATE(grade)  
+    BEGIN  
+        ROLLBACK TRANSACTION  
+    END  
+END  
+--********** End **********--
+go
+delete from score where sno='1001'
+go
+select * from score
+go
+select * from student
+go