Question

我有一个问题：

SELECT A.AHSHMT AS SHIPMENT, A.AHVNAM AS VENDOR_NAME, D.UNITS_SHIPPED, D.ADPON AS PO, B.NUMBER_OF_CASES_ON_TRANSIT, C.NUMBER_OF_CASES_RECEIVED FROM AHASNF00 A
      INNER JOIN (SELECT IDSHMT, COUNT(*) AS NUMBER_OF_CASES_ON_TRANSIT FROM IDCASE00 WHERE IDSTAT = '01' GROUP BY IDSHMT) B 
        ON (A.AHSHMT = B.IDSHMT) 
      LEFT JOIN (SELECT IDSHMT, (COUNT(*) AS NUMBER_OF_CASES_RECEIVED FROM IDCASE00 WHERE IDSTAT = '10' GROUP BY IDSHMT) C 
        ON (A.AHSHMT = C.IDSHMT) 
       INNER JOIN (SELECT ADSHMT, ADPON, SUM(ADUNSH) AS UNITS_SHIPPED FROM ADASNF00 GROUP BY ADSHMT, ADPON) D 
        ON (A.AHSHMT = D.ADSHMT) 
    WHERE A.AHSHMT = '540041134';

在第一个JOIN语句中，我有一个COUNT（*），在此计数中，有时我会得到NULL。我需要将其替换为“0-zero”，我知道我知道如何在SQL中执行此操作

ISNULL(COUNT(*), 0)

但是这对DB2不起作用，我该如何实现呢？你所有的帮助都非常感激。

Answer 1

在SELECT列表中的每个可空总计周围包裹COALESCE：

SELECT A.AHSHMT AS SHIPMENT, 
A.AHVNAM AS VENDOR_NAME, 
COALESCE( D.UNITS_SHIPPED, 0 ) AS UNITS_SHIPPED,
D.ADPON AS PO, 
COALESCE( B.NUMBER_OF_CASES_ON_TRANSIT, 0 ) AS NUMBER_OF_CASES_ON_TRANSIT, 
COALESCE( C.NUMBER_OF_CASES_RECEIVED, 0 ) AS NUMBER_OF_CASES_RECEIVED
FROM ...

您用于表达式B和D的内部联接意味着您将只接收来自A的行，这些行具有一个或多个传输中的案例（表达式B）并且在表达式D中具有一个或多个PO。是这样的您希望您的查询有效吗？

Answer 2

而不是使用ISNULL(COUNT(*), 0)，

尝试使用COALESCE(COUNT(*),0)

Answer 3

对DB2使用IFNULL(COUNT(*), 0)

当COUNT（*）在DB2中返回NULL时如何替换NULL

3 个答案: