sql 判断表是否存在，判断列是否存在 - sjns

sql 判断表是否存在，判断列是否存在

判断表是否存在：

语法：

SELECT  * FROM dbo.SysObjects where id = object_id(N\'表名\')  

 例子：

SELECT  * FROM dbo.SysObjects where id = object_id(N\'ExchangeLog\')

 

if exists(SELECT * FROM dbo.SysObjects where id = object_id(N\'ExchangeLog\'))
　　print \'表存在\'
else
　　print \'表不存在\'

 判断列是否存在：

语法：

select * from syscolumns where id=object_id(N\'表名\') and name =\'列名\'

 例子

select * from syscolumns where id=object_id(N\'ExchangeLog\') and name =\'Extype\'

 

if exists(select * from syscolumns where id=object_id(N\'ExchangeLog\') and name =\'Extype\')
	alter table ExchangeLog drop column ExType
else
begin
	alter table [ExchangeLog] add ExType nchar(15)
end
go