sql 分组后拼接字符串

    SELECT B.guid_m,LEFT(kh_ddcodeList,LEN(kh_ddcodeList)-1) as kh_ddcodeDetail FROM (
			SELECT guid_m,
			    (SELECT A1.kh_ddcode+', ' 
			     FROM (SELECT guid_m,kh_ddCode 
					   FROM  xsbillfh_d 
					   WHERE ISNULL(kh_ddcode,'')<>''
					   GROUP BY guid_m,kh_ddcode)  AS A1
			     WHERE A1.guid_m=A.guid_m AND ISNULL(kh_ddcode,'')<>''
			     FOR XML PATH('')) AS kh_ddcodeList
			FROM (SELECT guid_m,kh_ddCode 
			       FROM  xsbillfh_d 
			       WHERE ISNULL(kh_ddcode,'')<>''
			       GROUP BY guid_m,kh_ddcode  ) A 
			WHERE ISNULL(a.kh_ddcode,'')<>''
			GROUP BY guid_m
			) B