请前辈帮我看看这段代码为什么不对?

5454440

Select sum(金额)  FROM (Select 客户编码,sum(金额) as 金额 FROM (Select gl_accass.ccus_id as 客户编码,sum((case when gl_accass.cbegind_c<>N'贷' then gl_accass.mb else -gl_accass.mb end )) as 金额 FROM code INNER JOIN gl_accass ON code.ccode = gl_accass.ccode WHERE gl_accass.iperiod=1 and gl_accass.ccode like N'1133%'  and gl_accass.ccus_id is not null  Group by gl_accass.ccus_id order by gl_accass.ccus_id union Select GL_accvouch.ccus_id as 客户编码,sum(GL_accvouch.md-GL_accvouch.mc) as 金额 FROM code INNER JOIN gl_accvouch ON code.ccode = gl_accvouch.ccode WHERE GL_accvouch.iflag is null and iperiod<>0 and iperiod<13  and GL_accvouch.ccode like N'1133%' and dbill_date<=N'2008-12-31'   and GL_accvouch.ccus_id is not null  Group by GL_accvouch.ccus_id order by GL_accvouch.ccus_id) group by 客户编码) where 金额<0

meeting

1
用union联合的查询只能有一个order by
2
子查询必须用别名
如
select * from (select * from t) as a