触发器 完美运行

CREATE TRIGGER  NO5 ON SC  
FOR insert,delete,update 
AS 
declare @totalScore int 
declare @score1 int 
declare @score2 int 
declare @credit int 
declare @Cno char(4)  
declare @Sno char(10)  
 
select @score1=l.Grade from inserted l  
select @score2=l.Grade from deleted l/*修改时删掉的那个分数*/  
select @Cno=l.Cno from inserted l  
select @Sno=l.Sno from inserted l  
if(@score1>=60)  
begin 
select @credit=Ccredit from Course where Course.Cno=@Cno   
select @totalScore=(select totalScore from Student where Sno=@Sno)+@credit  
update Student  set totalScore=@totalScore where Sno=@Sno   
end 
 
if update(grade)  
begin 
select @score2=l.Grade from inserted l  
select @score1=l.Grade from deleted l/*修改时删掉的那个分数*/  
select @credit=Ccredit from Course where Course.Cno=@Cno   
select @Cno=l.Cno from inserted l  
select @Sno=l.Sno from inserted l  
if(@score1>60 and @score2<60)--把及格改成不及格  
update Student set totalScore=totalScore-@credit where Sno=@Sno   
else if(@score2>60 and @score1<60)--把不及格改成及格  
update Student set totalScore=totalScore+@credit where Sno=@Sno   
end