MSSQL 将字符类型字段做累加

数字性字段可以用sum()累加,而字符行字段就没办法用sum()

CREATE function f_sumchengp(@litm varchar(100)) 
returns varchar(8000) 
as 
begin 
declare @str varchar(8000) 
set @str='' 
select @str=@str+','+xmkitl from dbo.TMP_XM_038_BOM where xmlitm=@litm 
if(len(@str)>1)
    set @str=right(@str,len(@str)-1) 
return(@str)
end

XMLITM为需要group by的字段,xmkitl为需要累加的字段