sql

select 
a.client_no,--客户编号
a.part_no,--品号
a.cr_do_dlv_datetime,
sum(b.cr_do_qty)req_qty--排期需求数量
from cr_do a 
left outer join cr_do b on a.client_no=b.client_no and  a.part_no=b.part_no and a.cr_do_dlv_datetime>=b.cr_do_dlv_datetime
where b.part_no='000-3102200742' and b.client_no='C00199' 

group by a.client_no,a.part_no,a.cr_do_dlv_datetime

select的是a,sum的是B