citem_id iperiod mb
401 1 23520.00
401 2 256485.00
401 1 15642
需要查询分组citem_id,iperiod下最大值mb的语句：
SELECT citem_id,iperiod,mb,me,cbegind_c,cbegind_c_engl,ccode,cexch_name,cdept_id,cperson_id,ccus_id,csup_id,citem_class,md,mc,cendd_c,cendd_c_engl,mb_f,md_f,mc_f,me_f,nb_s,nd_s,nc_s,ne_s
FROM GL_accass tmp
WHERE (ccode = '218112')
and mb=me
and me>0
group by citem_id,iperiod,mb,me,cbegind_c,cbegind_c_engl,ccode,cexch_name,cdept_id,cperson_id,ccus_id,csup_id,citem_class,md,mc,cendd_c,cendd_c_engl,mb_f,md_f,mc_f,me_f,nb_s,nd_s,nc_s,ne_s
having (max(mb)>= all (select max(mb) from GL_accass where tmp.citem_id = citem_id and tmp.iperiod=iperiod group by citem_id,iperiod))
order by citem_id,iperiod
