sql 递归 STUFF

select distinct fm_id,
STUFF((select distinct ISNULL( ',' +SO_Num,''  ) from [t_BADItems] it WHERE it.fm_id=its.fm_id for xml path('') ),1,1,'') AS SO_Nums 
 from [dbo].[t_BADItems] its

 表内一对多 的关系查询