sql server 触发器

 1 /*例：下例说明inserted表和deleted表的作用*/
 2 
 3 if exists(select name from sysobjects where name=‘trig_2‘ and type=‘TR‘)
 4     drop trigger trig_2
 5 go
 6 
 7 create trigger trig_2 
 8 on student
 9 after update                         --update触发器
10 as 
11     print ‘inserted表‘
12     select * from inserted
13     print ‘deleted表‘
14     select * from deleted
15 go
16 set nocount on
17 update student set sname=‘关二‘ where sno=2
18 --drop trigger trig_2
19 
20 
21 create trigger trig_3 
22 on student
23 after insert                         --insert触发器
24 as 
25     print ‘inserted表‘
26     select * from inserted
27     print ‘deleted表‘
28     select * from deleted
29 go
30 insert student values(100,‘刘一百‘,‘男‘,25)
31 drop trigger trig_3
32 
33 
34 create trigger trig_4 
35 on student
36 after delete                         --delete触发器
37 as 
38     print ‘inserted表‘
39     select * from inserted
40     print ‘deleted表‘
41     select * from deleted
42 go
43 delete student where sno=100
44 drop trigger trig_4

 1 /*DDL触发器*/
 2 
 3 /*在test数据库上创建一个DDL触发器safe，
 4 用来防止数据库中的任一表被修改或删除。*/
 5 
 6 create trigger safetest
 7 on database                         --数据库DDL触发器
 8 after drop_table,alter_table
 9 as
10 begin
11     raiserror(‘不能修改表结构‘,16,2)
12     rollback
13 end
14 go
15  
16 --执行以下程序，观察结果
17 alter table student add nation char(10)
18 
19 disable trigger safetest on database
20 drop trigger safetest on database
21 ---------------------------------------------------------
22 
23 
24 /*在服务器上创建一个DDL触发器tablecreat，
25 用来防止在服务器上创建数据库*/
26 
27 create trigger trig_last
28 on all server
29 after create_database
30 as
31 begin
32     raiserror(‘不能创建新的数据库‘,16,2)
33     rollback
34 end
35 go
36 
37 --执行以下程序，观察结果
38 create database test_trig
39 
40 disable trigger trig_last on all server
41 drop trigger trig_last on all server

 1 /*触发器禁用和启用*/
 2 
 3 /*禁用sc表上的触发器trig_g。*/
 4 alter table sc disable trigger trig_g
 5 disable trigger trig_g on sc
 6 go
 7 
 8 /*启用sc表上的触发器trig_g。*/
 9 alter table sc enable trigger trig_g
10 enable trigger trig_g on sc
11 go
12 
13 --执行以下程序，观察结果
14 insert into sc values(1,100,1,-50)
15 select * from sc

 1 /*具体应用*/
 2 
 3 /*创建触发器trig3，
 4 当删除student表中的学生记录时，
 5 应该同时删除sc表中对应的记录*/
 6 
 7 create trigger trig_5
 8 on student
 9 for delete
10 as 
11  delete sc
12  where sc.sno in(select sno from deleted)
13 go
14 
15 select * from student
16 select * from sc
17 go
18 
19 /*exec sp_help score   --查看其中外键
20 
21 alter table score         --删除外键
22 drop CONSTRAINT FK_score_course
23 
24 alter table score
25 drop CONSTRAINT FK_score_student*/
26 
27 
28 delete student where sno=3
29 go
30 
31 select * from student
32 select * from sc 
33 -------------------------------------------------------------
34 
35 
36 create trigger trig_g 
37 on sc
38 after insert,update
39 as
40 begin
41     declare @g int
42     select @g=grade from inserted
43     if @g<0
44     begin
45          select ‘成绩必须>=0‘
46          rollback
47     end
48 end
49 go
50 
51 --执行以下程序，观察结果
52 insert into sc values(1,10,1,50)
53 select * from sc
54 
55 
56 /*例: 建立一个修改触发器trigno，
57 该触发器防止用户修改表student的学号*/
58 
59 create trigger trigno
60 on student
61 after update
62 as
63 if update(sno)
64     begin
65         raiserror(‘不能修改学号‘,16,2)
66         rollback
67     end
68 go
69 
70 --执行以下程序，观察结果
71 update student set sno=‘2‘ where sno=‘1‘
72 select * from student
73 ------------------------------------------------------
74 
75 
76 /*INSTEAD OF触发器*/
77 
78 /*例：在student表上创建一个INSTEAD OF触发器trig_6，
79 当用户插入数据时注意观察触发器的执行。*/
80 
81 create trigger trig_6
82 on student
83 instead of insert
84 as
85     select * from student
86 go
87 
88 --执行以下程序，观察结果
89 insert into student(sno,sname) values(‘300‘,‘白扯‘)