向各位请教一下，详见内部

[vcforever]

语句：
select * from Z_TJ_JHGL_CAIFAJIHUA as c,
(select * from
(select
NF,XMDM,JLDW,Count(*) as SL
from Z_TJ_JHGL_CAIFAJIHUA
group by
NF,XMDM,JLDW
) as a where SL=1) as b
where
c.NF=b.NF and c.XMDM=b.XMDM and c.JLDW=b.JLDW
能够正常执行，而语句：
select * from
(

---下面为上面的语句-------------------------
select * from Z_TJ_JHGL_CAIFAJIHUA as c,
(select * from
(select
NF,XMDM,JLDW,Count(*) as SL
from Z_TJ_JHGL_CAIFAJIHUA
group by
NF,XMDM,JLDW
) as a where SL=1) as b
where
c.NF=b.NF and c.XMDM=b.XMDM and c.JLDW=b.JLDW
---结束--------------------------------------

) as a
order by
NF,XMDM,JLDW
不能够执行，请问是什么原因呢？