Informix除以零错误

我有一个错误除以零错误的查询。我已经隔离了查询中哪些错误的部分，并尝试使用NVL进行修复，但进展不顺利，有人可以发现我的错误吗？

select  warehouse.ware_code,
    warehouse.desc_text,
    maingrp.maingrp_code,
    maingrp.desc_text,
    prodgrp.prodgrp_code,
    prodgrp.desc_text,
    left(product.part_code,7) Parent_Product_code,
    product.part_code,
    product.desc_text,
    sum(salesstat.order_qty - salesstat.return_qty) Total_Sales,
    sum((salesstat.order_qty - salesstat.return_qty) / 6) Average_Weekly_Sales,
    sum(((salesstat.order_qty - salesstat.return_qty) / 6) * 4) Average_Monthly_Sales,
    '??' Note,
    sum(prodstatus.onhand_qty) Stock_On_Hand,
    sum(orderstat.order_qty - orderstat.cancel_qty) Outstanding_orders,
    sum(prodstatus.onhand_qty - (orderstat.order_qty - orderstat.cancel_qty)) Stock_Available,
    --CASE
    --WHEN nvl(sum(salesstat.order_qty - salesstat.return_qty),0) = 0
    --  THEN 999
    --ELSE  sum(prodstatus.onhand_qty / ((salesstat.order_qty - salesstat.return_qty) / 6))
    --END as Weeks_Stock_Remaining,
    '??' Stock_ordered,
    '??' Production_date
from
    warehouse,
    warereptdetl,
    maingrp,
    prodgrp,
    product,
    prodstatus,
    salesstat,
    orderstat,
    Statint
where   warehouse.cmpy_code = maingrp.cmpy_code
and warehouse.cmpy_code = warereptdetl.cmpy_code
and warehouse.cmpy_code = prodgrp.cmpy_code
and warehouse.cmpy_code = product.cmpy_code
and warehouse.cmpy_code = salesstat.cmpy_code
and warehouse.cmpy_code = prodstatus.cmpy_code
and warehouse.cmpy_code = orderstat.cmpy_code
and warehouse.cmpy_code = statint.cmpy_code
and product.ware_code = prodstatus.ware_code
and product.ware_code = warehouse.ware_code
and product.ware_code = salesstat.ware_code
and product.ware_code = orderstat.ware_code
and product.ware_code = warereptdetl.ware_code
and product.part_code = salesstat.part_code
and product.part_code = orderstat.part_code
and product.part_code = prodstatus.part_code
and product.prodgrp_code = salesstat.prodgrp_code
and product.prodgrp_code = orderstat.prodgrp_code
and product.prodgrp_code = prodgrp.prodgrp_code
and product.maingrp_code = salesstat.maingrp_code
and product.maingrp_code = orderstat.maingrp_code
and product.maingrp_code = maingrp.maingrp_code
and salesstat.year_num = statint.year_num
and salesstat.int_num = statint.int_num
and salesstat.stat_type_code = statint.type_code
and orderstat.year_num = statint.year_num
and orderstat.int_num = statint.int_num
and orderstat.stat_type_code = statint.type_code
and warehouse.cmpy_code = 'AB'
and warereptdetl.warereptgrp_code = 'NSW'
and product.ware_code = 'HP1'
and product.status_ind <> 3
and left(product.part_code,2) = '21'
and statint.year_num = 2016
and statint.int_num between 29 AND 34
--and   statint.int_num = 29
and statint.type_code = 'WLY'
Group by 1,2,3,4,5,6,7,8,9

注释掉的部分是我尝试进行修复的地方，如果我注释掉，则查询运行正常（尽管有点慢）。

问题的第二部分是在没有访问我的数据库的情况下您可能无法回答的问题，但是如果我运行查询1、2甚至3周（statint.int_num），查询将在不到1分钟的时间内返回。一旦我将其推迟6周（这就是我所需要的），查询就需要40多分钟才能返回结果。

我在查询中的任何地方都看不到创建笛卡尔坐标的地方，但是盯着它看了这么长时间，以至于我可能会错过它。