oracle查询group by视图报错

select t.yydm,
t.yydj,
t.jsny,
t.xzlbzh xzlb/*,
(select item_name
from tb_dic_fyshjs_bblb
where item_id = t.xzlbzh
and valid_flag = '1') xzlbmc*/
from (select YYDM,
(select yljgmc from tb_dic_ddyljg where yljgdm = yydm) yymc,
(select yljglbmc
from yboltp.TB_DIC_DDYLJG_YLJGLB@oltpsync
where yljglb =
trim(pk_common_fyshjs.func_GetDDJGZB(a.yydm, '0009'))
and yljgzlb =
trim(pk_common_fyshjs.func_GetDDJGZB(a.yydm, '0010'))) yydj,
JSNY,
decode(xzlb,
'1',
'01',
'2',
'01',
'6',
'01',
'3',
'02',
'4',
'03',
'5',
'03',
'7',
'04',
'8',
'04',
xzlb) xzlbzh
from tb_fyshjs_zyyp a
where 1 = 1
group by yydm,
decode(xzlb,
'1',
'01',
'2',
'01',
'6',
'01',
'3',
'02',
'4',
'03',
'5',
'03',
'7',
'04',
'8',
'04',
xzlb),
jsny) t

查询注释部分

/*,
(select item_name
from tb_dic_fyshjs_bblb
where item_id = t.xzlbzh
and valid_flag = '1') xzlbmc*/
就会报错，显示不是分组函数。但是查询视图的xzlbzh字段是不会报错的，当把它作为子查询的条件时才会报错，且视图查询完全没问题，困扰了很久，至今不知道原因。