exists的用法如下：

1、判斷數(shù)據(jù)庫(kù)是否存在

if exists (select*fromsysdatabaseswherename= '數(shù)據(jù)庫(kù)名')

dropdatabase[數(shù)據(jù)庫(kù)名]

2、判斷表是否存在

if not exists (select * from sysobjects where [name] = '表名' and xtype='U')

begin

--這里創(chuàng)建表

end

3、判斷存儲(chǔ)過(guò)程是否存在

if exists (select*fromsysobjectswhereid = object_id(N'[存儲(chǔ)過(guò)程名]') and OBJECTPROPERTY(id, N'IsProcedure') = 1)

dropprocedure[存儲(chǔ)過(guò)程名]

4、判斷視圖是否存在

（1）SQL Server 2000

IF EXISTS (SELECT*FROMsysviewsWHEREobject_id = '[dbo].[視圖名]'

（2）SQL Server 2005

IF EXISTS (SELECT*FROMsys.viewsWHEREobject_id = '[dbo].[視圖名]'

5、判斷函數(shù)是否存在

if exists (select*fromdbo.sysobjectswhereid = object_id(N'[dbo].[函數(shù)名]') and xtype in (N'FN', N'IF', N'TF'))

dropfunction[dbo].[函數(shù)名]

擴(kuò)展資料

SQL的提升

1、復(fù)制表(只復(fù)制結(jié)構(gòu)，源表名：a 新表名：b) (Access可用)

法一：select * into b from a where 1<>1

法二：select top 0 * into b from a

2、拷貝表(拷貝數(shù)據(jù),源表名：a 目標(biāo)表名：b) (Access可用)

insert into b(x, y, z) select d,e,f from a;

3、跨數(shù)據(jù)庫(kù)之間表的拷貝(具體數(shù)據(jù)使用絕對(duì)路徑) (Access可用)

insert into b(x, y, z) select d,e,f from a in ‘具體數(shù)據(jù)庫(kù)’ where 條件

例子：。.from b in '"&Server.MapPath("."&"\data.mdb" &"' where..

4、子查詢(表名1：a 表名2：b)

select a,b,c from a where a IN (select d from b 或者： select a,b,c from a where a IN (1,2,3)

5、顯示文章最后時(shí)間

select a.title,a.username,b.adddate from table a,(select max(adddate) adddate from table where table.title=a.title) b