我正在使用sum case处理mysql查询。该查询适用于某些情况，但不适用于一种情况。
select orders.orderid, campers.description, dealers.name, orders.act_delivery,
sum(case orderitems.std
when 0 then
(case when orderitems.price = 0 then retail_price.price * orderitems. qty else orderitems.price * orderitems.qty end)
when 1 then
(case when orderitems.origqty = 0 then
0 else
(case when orderitems.price = 0
then retail_price.price * (orderitems.qty - orderitems.origqty)
else orderitems.price * (orderitems.qty - orderitems.origqty)
end)
end)
when 2 then
0
else
(case when orderitems.deletedprice = 0 then retail_price.price * orderitems. qty else orderitems.deletedprice * orderitems.qty end)
end) as retail
from orderitems, orders, dealers, campers, products, retail_price
where orderitems.orderid = orders.orderid
and orderitems.productid = products.prodid
and orderitems.productid =retail_price.prodid
and orders.dealerid = retail_price.dealer
and orders.dealerid = dealers.dealerid
and orders.camper = campers.camperid
and act_delivery > 0
and orderitems.std in (0, 1, 2)
and orders.dealerid not in (1, 9, 10, 12,15,16)
and spares_od = 0
and orders.act_delivery > '2016-10-01'
and orders.act_delivery <= '2016-10-31'
group by orders.orderid,orders.dealerid, orders.act_delivery order by orders.act_delivery, orders.orderid
当orderitems.std = 3时会出现问题。在任何一种情况下，我都无法得到结果。
所有其他情况似乎都正常。