触发器的概念：它是由事件驱动的，就像java中的监听，当某个事件发生了，就会做一些工作。
下面直接上干货，创建insert触发器、delete触发器、DDL触发器和如何查看触发器定义
1.创建三个表学生表、班级表、课程表
create database student_score
GO
--在数据库中创建三个表学生表、班级表、课程表的结构
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.插入用例数据
--往表中插入数据(student,course,score)
insert into student values('0601001','李玉','女','1987-05-06', '0601')
insert into student values('0601002','鲁敏','女','1988-06-28', '0601')
insert into student values('0601003','李小路','女','1987-01-08', '0601')
insert into student values('0601004','鲁斌','男','1988-04-21', '0601')
insert into student values('0601005','王宁静','女','1986-05-29', '0601')
insert into student values('0601006','张明明','男','1987-02-24', '0601')
insert into student values('0601007','刘晓玲','女','1988-12-21', '0601')
insert into student values('0601008','周晓','男','1986-04-27', '0601')
insert into student values('0601009','易国梁','男','1985-11-26', '0601')
insert into student values('0601010','季风','男','1986-09-21', '0601') insert into class values('0501','计算机办公应用', 40)
insert into class values('0502','网络构建', 43)
insert into class values('0503','图形图像', 48)
insert into class values('0601','可视化', 41)
insert into class values('0602','数据库', 38)
insert into class values('0603','网络管理', 45)
insert into class values('0604','多媒体', 40)
insert into class values('0701','计算机办公应用', 39)
insert into class values('0702','WEB应用', 38)
insert into class values('0703','网络构建', 40) insert into course values('001','计算机应用基础')
insert into course values('002','关系数据基础')
insert into course values('003','程序设计基础')
insert into course values('004','数据结构')
insert into course values('005','网页设计')
insert into course values('006','网站设计')
insert into course values('007','SQL Server 2000关系数据库')
insert into course values('008','SQL Server 2000程序设计')
insert into course values('009','计算机网络')
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.练习实例
--1）在student上创建INSERT触发器stu_insert，要求在student表中插入记录时(要求每次只能插入一条记录)，这个触发器都将更新class表中的class_nun列。并测试触发器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) --测试
insert into student values('0602011','文','女','1986-09-21', '0602') --2）在student上创建DELETE触发器stu_delete，要求在student表中删除记录时，这个触发器都将更新class表中的class_nun列。并测试触发器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) --测试
delete from student where stu_id='0601001' --3）查看触发器相关信息:使用系统存储过程sp_help，sp_helptext查看触发器相关信息。
exec sp_help
exec sp_help stu_insert
exec sp_helptext stu_insert --4）对于下列触发器：
create trigger stu_update
on student
instead of update
as
print '修改学生表'
drop trigger stu_update
执行语句
update student
set stu_id='0601003'
where stu_name='鲁斌'
会怎么样？
--消息 2627，级别 14，状态 1，第 1 行
--违反了 PRIMARY KEY 约束 'PK__student__E53CAB217F60ED59'。不能在对象 'dbo.student' 中插入重复键。
--语句已终止。 --5）创建DDL触发器，在当前数据库中不允许删除或修改表
create trigger data
on database
for drop_table, alter_table
as
print '不允许删除或修改表'
rollback
此例很完整，供有需要进行练习触发器的朋友看看