怎样把一张表中一列的值，赋值给一个变量.

[123liuhh]

例：
表
　aa bb cc
12 a 0
13 b 0
15 c 0

把aa列的内容赋值给一个变量,就好一条sql语句完成.
得到结果：
　变量　＠sql = '12,13,15'

[liangCK]

DECLARE @re varchar(100)
	SET @re=''
	SELECT @re=@re+','+CAST(col2 as varchar)
	FROM tb
	WHERE col1=@col1

[hery2002]

    DECLARE @RtnVal nvarchar(2000)
    SET @RtnVal =''
    SELECT @RtnVal =@RtnVal +','+CAST(aa as nvarchar)   FROM tb
    SELECT @RtnVal 

[pt1314917]

declare @sql varchar(100)
select @sql=isnull(@sql+',','')+ltrim(aa) FROM 表名
select  @sql

[ojuju10]

DECLARE @RtnVal nvarchar(2000)
SET @RtnVal =''
SELECT @RtnVal =@RtnVal +','+ltrim(aa) FROM tb
SELECT @RtnVal

[dawugui]

--方法一
declare @sql varchar(1000)
set @sql = ''
select @sql = @sql + t.aa + ',' from (select aa from tb) as t
set @sql='select result = ''' + left(@sql , len(@sql) - 1) + ''''
exec(@sql)


--方法二
declare @output varchar(8000)
select @output = coalesce(@output + ',' , '') + aa from tb
print @output