求和NULL或将NULL转换为0以求和sql db2.iseries

我是SQL的新手，目前正在尝试查询DB2.iSeries数据库，我被卡住了

这是我的代码：

SELECT IPROD, IDESC, IMRP, NONAV
FROM

(SELECT IPROD, IDESC, IMRP FROM IIM WHERE IBUYC IN (<pln.value>) AND IMRP = 'N') AS IM

INNER JOIN
(SELECT I01PROD FROM INV01P
WHERE I01SUPS = '0'
AND I01SUPP = '0')
AS L1 ON IM.IPROD = L1.I01PROD

LEFT OUTER JOIN
(SELECT WPROD, SUM(WOPB-WISS+WADJ+WRCT) AS NONAV FROM IWI
WHERE LEFT(WWHS,1) = '9'
GROUP BY WPROD) AS L2 ON IM.IPROD = L2.WPROD

GROUP BY IPROD, IDESC, IMRP, NONAV
HAVING SUM(NONAV) = 0

ORDER BY IPROD
FETCH FIRST 10000 ROWS ONLY

这是我的代码，在查询时可以很好地工作：sumnanav=0，但我的问题是有些产品的值为NULL，我也需要提取这些值

我在查询的不同点尝试了IFNULL，但失败了

我知道如何将字段输出视图设置为0，但当涉及到求和时，它无法提取这些乘积

有人能帮我在字段求和后提取NULL和0值吗

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谢谢

现在您只需优化内部选择，我不太明白您的意思

SELECT IPROD, IDESC, IMRP, NONAV
FROM

(SELECT IPROD, IDESC, IMRP FROM IIM WHERE IBUYC IN (<pln.value>) AND IMRP = 'N') AS IM

INNER JOIN
(SELECT I01PROD FROM INV01P
WHERE I01SUPS = '0'
AND I01SUPP = '0')
AS L1 ON IM.IPROD = L1.I01PROD

LEFT OUTER JOIN
(SELECT WPROD, SUM(WOPB-WISS+WADJ+WRCT) AS NONAV FROM IWI
WHERE LEFT(WWHS,1) = '9'
GROUP BY WPROD) AS L2 ON IM.IPROD = L2.WPROD

GROUP BY IPROD, IDESC, IMRP, NONAV
HAVING SUM(COALESCE(NONAV,0)) = 0

ORDER BY IPROD
FETCH FIRST 10000 ROWS ONLY