1:
普通SQL语句可以用Exec执行
eg: Select * from tableName
Exec(''''select * from tableName'''')
sp_executesql N''''select * from tableName'''' -- 请注意字符串前一定要加N
2:
字段名,表名,数据库名之类作为变量时,必须用动态SQL
eg:
declare @fname varchar(20)
set @fname = ''''[name]''''
Select @fname from sysobjects -- 错误
Exec(''''select '''' + @fname + '''' from sysobjects'''') -- 请注意 加号前后的 单引号的边上要加空格
exec sp_executesql N'''' select '''' + @fname + '''' from sysobjects''''
当然将字符串改成变量的形式也可
declare @s varchar(1000)
set @s = ''''select '''' + @fname + '''' from sysobjects''''
Exec(@s) -- 成功
exec sp_executesql @s -- 此句会报错
declare @s Nvarchar(1000) -- 注意此处改为nvarchar(1000)
set @s = ''''select '''' + @fname + '''' from sysobjects''''
Exec(@s) -- 成功
exec sp_executesql @s -- 此句正确,
3: 输出参数
eg:
declare @num,
@sqls
set @sqls=''''select count(*) from '''' + @servername + ''''.a.dbo.b''''
exec(@sqls)
我如何能将exec执行的结果存入变量@num中
declare @num int,
@sqls nvarchar(4000)
set @sqls=''''select @a=count(*) from ''''+@servername+''''.a.dbo.b''''
exec sp_executesql @sqls,N''''@a int output'''',@num output
select @num