觸發器的概念：它是由事件驅動的，就像java中的監聽，當某個事件發生了，就會做一些工作。

下面直接上乾貨，建立insert觸發器、delete觸發器、DDL觸發器和如何檢視觸發器定義

1.建立三個表學生表、班級表、課程表

create database student_score
GO
--在資料庫中建立三個表學生表、班級表、課程表的結構
use student_score
GO
create table student
( stu_id char(8) primary key,
  stu_name char(10),
  stu_sex char(2),
  stu_birthday smalldatetime,
  class_id char(6)
)
go
create table class
(  class_id char(6) primary key,
  class_name varchar(30),
class_num int,
)
create table course
( course_id char(3) primary key,
  course_name varchar(30),
)
go
create table score
( stu_id char(8),
  course_id char(3),
  score int check(score>=0 and score<=100)
  primary key(stu_id,course_id)
)
go
 

 2.插入用例資料

--往表中插入資料(student,course,score)
 insert into student values('0601001','李玉','女','1987-05-06', '0601')
 insert into student values('0601002','魯敏','女','1988-06-28', '0601')
 insert into student values('0601003','李小路','女','1987-01-08', '0601')
 insert into student values('0601004','魯斌','男','1988-04-21', '0601')
 insert into student values('0601005','王寧靜','女','1986-05-29', '0601')
 insert into student values('0601006','張明明','男','1987-02-24', '0601')
 insert into student values('0601007','劉曉玲','女','1988-12-21', '0601')
 insert into student values('0601008','周曉','男','1986-04-27', '0601')
 insert into student values('0601009','易國樑','男','1985-11-26', '0601')
 insert into student values('0601010','季風','男','1986-09-21', '0601')
  
insert into class values('0501','計算機辦公應用', 40)
insert into class values('0502','網路構建', 43)
insert into class values('0503','圖形影象', 48)
insert into class values('0601','視覺化', 41)
insert into class values('0602','資料庫', 38)
insert into class values('0603','網路管理', 45)
insert into class values('0604','多媒體', 40)
insert into class values('0701','計算機辦公應用', 39)
insert into class values('0702','WEB應用', 38)
insert into class values('0703','網路構建', 40)
 
insert into course values('001','計算機應用基礎')
insert into course values('002','關係資料基礎')
insert into course values('003','程式設計基礎')
insert into course values('004','資料結構')
insert into course values('005','網頁設計')
insert into course values('006','網站設計')
insert into course values('007','SQL Server 2000關係資料庫')
insert into course values('008','SQL Server 2000程式設計')
insert into course values('009','計算機網路')
insert into course values('010','Windows Server 配置')
 
insert into score values('0601001','001',78)
insert into score values('0601002','001',88)
insert into score values('0601003','001',65)
insert into score values('0601004','001',76)
insert into score values('0601005','001',56)
insert into score values('0601006','001',87)
insert into score values('0601007','001',67)
insert into score values('0601008','001',95)
insert into score values('0601009','001',98)
insert into score values('0601010','001',45)
 
insert into score values('0601001','002',48)
insert into score values('0601002','002',68)
insert into score values('0601003','002',95)
insert into score values('0601004','002',86)
insert into score values('0601005','002',76)
insert into score values('0601006','002',57)
insert into score values('0601007','002',77)
insert into score values('0601008','002',85)
insert into score values('0601009','002',98)
insert into score values('0601010','002',75)
 
insert into score values('0601001','003',88)
insert into score values('0601002','003',78)
insert into score values('0601003','003',65)
insert into score values('0601004','003',56)
insert into score values('0601005','003',96)
insert into score values('0601006','003',87)
insert into score values('0601007','003',77)
insert into score values('0601008','003',65)
insert into score values('0601009','003',98)
insert into score values('0601010','003',75)
 
insert into score values('0601001','004',74)
insert into score values('0601002','004',68)
insert into score values('0601003','004',95)
insert into score values('0601004','004',86)
insert into score values('0601005','004',76)
insert into score values('0601006','004',67)
insert into score values('0601007','004',77)
insert into score values('0601008','004',85)
insert into score values('0601009','004',98)
insert into score values('0601010','004',75)
 
insert into score values('0601001','005',74)
insert into score values('0601002','005',68)
insert into score values('0601005','005',76)
insert into score values('0601008','005',85)
insert into score values('0601009','005',98)
insert into score values('0601010','005',75)
 
insert into score values('0601002','006',88)
insert into score values('0601003','006',95)
insert into score values('0601006','006',77)
insert into score values('0601008','006',85)
insert into score values('0601010','006',55)
 
insert into score values('0601001','007',84)
insert into score values('0601002','007',68)
insert into score values('0601003','007',95)
 
insert into score values('0601004','008',86)
insert into score values('0601005','008',76)
insert into score values('0601006','008',67)
 
insert into score values('0601007','009',67)
insert into score values('0601008','009',85)
 
insert into score values('0601009','010',98)
insert into score values('0601010','010',75)
 

3.練習例項

--1）在student上建立<strong>INSERT觸發器</strong>stu_insert，要求在student表中插入記錄時(要求每次只能插入一條記錄)，這個觸發器都將更新class表中的class_nun列。並測試觸發器stu_insert。
create trigger stu_insert
on student
for insert
as
update class set class_num=class_num + 1
where class_id=(select class_id from inserted)
 
--測試
insert into student values('0602011','文','女','1986-09-21', '0602')
 
 
--2）在student上建立<strong>DELETE觸發器</strong>stu_delete，要求在student表中刪除記錄時，這個觸發器都將更新class表中的class_nun列。並測試觸發器stu_delete。
create trigger stu_delete
on student
for delete 
as
update class set class_num=class_num - 1
where class_id = (select class_id from deleted)
 
--測試
delete from student where stu_id='0601001'
 
--3）檢視觸發器相關資訊:使用系統儲存過程<strong>sp_help，sp_helptext檢視觸發器</strong>相關資訊。
exec sp_help
exec sp_help stu_insert
exec sp_helptext stu_insert
 
--4）對於下列觸發器：
create trigger stu_update
on student
instead of update
as
print '修改學生表'
drop trigger stu_update
執行語句
update student
set stu_id='0601003'
where stu_name='魯斌'
會怎麼樣？
--訊息 2627，級別 14，狀態 1，第 1 行
--違反了 PRIMARY KEY 約束 'PK__student__E53CAB217F60ED59'。不能在物件 'dbo.student' 中插入重複鍵。
--語句已終止。
 
--5）建立<strong>DDL觸發器</strong>，在當前資料庫中不允許刪除或修改表
create trigger data
on database
for drop_table, alter_table
as
print '不允許刪除或修改表'
rollback