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常用SQL语句收藏 <三>

2015-09-06 15:32 369 查看

视图的创建删除与使用

创建:
create view view_1 as SELECT     dbo.class.class, dbo.class.studentnumber, dbo.class.teacher, dbo.student.id, dbo.student.name, dbo.student.age, dbo.student.english,
dbo.student.born, dbo.student.class AS Expr1
FROM         dbo.class INNER JOIN
dbo.student ON dbo.student.class = dbo.class.class
使用: select * from view_1
删除:drop view view_1


触发器创建

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go
CREATE  TRIGGER [trigger_1]
ON  [dbo].[class]
AFTER DELETE
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
delete from dbo.student where dbo.student.class not in (select class from dbo.class)
-- Insert statements for trigger here
END


此触发器的功能是:当class表有删除操作时,同步student表中的记录,将不存在的班级的记录全部删除.

使用触发器:

—altertable student drop CONSTRAINT  FK_CLASS
—select* From student where class='chuyi'
—select* From class where class='chuyi'
—deletefrom class where class='chuyi'
—select* From student where class='chuyi'
—select* From class where class='chuyi‘
—可以看到student表中的记录也被更新了.


修改触发器

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go
ALTER TRIGGER  [trigger_1]
ON  [dbo].[class]
AFTER DELETE
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
delete from dbo.student where dbo.student.class not in (select class from dbo.class)
-- Insert statements for trigger here

END


删除触发器:Drop trigger trigger_1
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