小问题?关于赋值

[xingfuniao]

declare @tablename varchar(50)
declare @tableidname varchar(50)
declare @maxid varchar(50)
declare @tmp varchar(500)

set @tablename='tbMember_Dept'
set @tableidname='mdID'

set @tmp='select max('+@tableidname+') from '+@tablename


我想把最大的ID号,赋值给@maxid,要怎么做??

[rucypli]

set @tmp='select @maxid =max('+@tableidname+') from '+@tablename

[--小F--]

输出参数 
declare @num int, @sqls nvarchar(4000) 
set @sqls='select count(*) from tableName' 
exec(@sqls) 

--如何将exec执行结果放入变量中？ 

declare @num int, @sqls nvarchar(4000) 
set @sqls='select @a=count(*) from tableName ' 
exec sp_executesql @sqls,N'@a int output',@num output 
select @num 

[jwdream2008]

set @tmp=exec('select max('+@tableidname+') from '+@tablename) 

[百年树人]

set @tmp=N'select @maxid=max('+@tableidname+') from '+@tablename 

exec sp_executesql @tmp,N'@maxid varchar(50) output',@maxid varchar(50)

[xingfuniao]

搞定,谢谢各位
exec sp_executesql @tmp,N'@maxid varchar(50) output',@maxid output