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为Students创建一触发器,并给出正反实例的SQL语句:当插入或修改一条学生记录时,确保此学生的入学年龄在14~40岁之间。
create trigger TRIGGER_Stu on Students for insert , update as declare @age int select @age=year(getdate())-year(Sbirth) from inserted if @age not between 14 and 40 begin print '不符合年龄条件' rollback transaction end
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为Teachers表创建一触发器,并给出正反实例的SQL语句:男职工年龄不能超过60岁,女职工职称是“教授”的年龄不能超过60岁,其他女职工年龄不能超过55岁
create trigger trigger_teach on Teachers for insert as declare @age int declare @gender varchar(2) declare @prof varchar(20) select @age=(year(getdate())-year(Tbirth)), @gender=Tgender,@prof=Tprof from inserted if @gender = '男' or (@gender='女' and @prof='教授') begin if @age > 60 --begin print '超龄' rollback transaction --end end else if(@gender = '女') begin if(@age>55) --begin print '超龄' rollback transaction --end end
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为Teachers创建一触发器,并给出正反实例的SQL语句:当职称从“讲师”晋升为“副教授”时,岗位津贴(TComm)自动增加500元;从“副教授”晋升为“教授”时,岗位津贴自动增加900元;不允许越级晋升,也不能降级。
create trigger trigger_teacher_prof on Teachers for update as declare @tno varchar(20) declare @up_prof varchar(20) declare @old_prof varchar(20) select @up_prof=Tprof,@tno=Tno from inserted select @old_prof from deleted if(@old_prof='讲师' and @up_prof='副教授') begin update Teachers set Tcomm=Tcomm+500 where Tno=@tno end else if(@old_prof='副教授' and @up_prof='教授') begin update Teachers set Tcomm=Tcomm+900 where Tno=@tno end else if ((@old_prof='讲师' and @up_prof in ('讲师','副教授')) or (@old_prof='助教' and @up_prof in ('助教','讲师'))) begin print '不允许越级晋升' rollback transaction end
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为Reports表创建一触发器,并给出正反实例的SQL语句:当插入一条记录或修改成绩时,若记录不为空,则须确保此记录的成绩在0~100分之间
create trigger TRIGGER_Rpt on Reports for insert,update as declare @grade decimal(5,2) select @grade=Grade from inserted if(@grade not between 0 and 100) begin print '成绩插入有误' rollback transaction end
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为选课表Reports增加一个属性列Level,并为该表创建一触发器,将成绩Grade按下列对应关系由分数转换成等级,并保存到Level列中:
小于60分:不及格 60~70分:及格
70 ~ 80分:中 80 ~ 90分:良
90分以上:优alter table Reports add Re_Level varchar(10)
- 如果直接使用语句设置变量值的话需要加set关键字
create trigger TRIGGER_Rep on Reports for insert , update as declare @grade decimal(4,1) declare @level varchar(10) select @grade=Grade from inserted if(@grade between 60 and 70) begin set @level='及格' end else if(@grade between 60 and 70) begin set @level='优' end else begin set @level='不及格' end update Reports set Re_Level=@level
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创建一个学分表StuCredits,包含两个属性列(学号Sno,总学分TotalCredits),用来保存学生已获得的总学分数。
为选课表Reports创建一触发器:当增加一条记录或修改成绩Grade时,重新统计该名学生获得的总学分,并将结果保存到StuCredits表中
① 当StuCredits表为空时,更新Reports表中的某条选课记录的成绩,然后查询StuCredits表中的数据;
② 当StuCredits表不为空时,选择该表中已有的某位学生,然后在Reports表中新增一条该学生的选课记录,并给出成绩(>=60),然后再查询StuCredits表中,该为学生总学分的变化。create table StuCredits( Sno char(12) primary key, TotalCredits int )
create trigger reports_credits on Reports for insert,update as declare @sno char(12) declare @credit int select @sno=Sno from inserted select @credit=sum(C.Ccredit) from Reports R, Courses C where R.Cno = C.Cno and R.Sno = @sno and R.Grade > 60 if(not exists(select * from StuCredits where Sno = @sno)) begin insert into StuCredits values(@sno,isnull(@credit,0)) end else begin update StuCredits set TotalCredits = isnull(@credit,0) where Sno=@sno end