Question

所以我有以下代码

SELECT PICK_SO_NUMBER, CUSTOMER, SO_PRODUCT, DO_QUANTITY, DO_PACKING, DO_DATE,
COALESCE(INVOICED_QTY, 0) AS INVOICED_QTY, 
DO_QUANTITY-INVOICED_QTY AS NOT_INVOICED, 
INVOICE_PACKING 
FROM VW_TRAFFIC_PO_SIDE
WHERE  DO_QUANTITY > INVOICED_QTY OR (INVOICED_QTY IS NULL AND DO_QUANTITY IS NOT NULL)

合并下面的行假设从INVOICED_QTY中减去DO_QUANTITY，但是当INVOICED_QTY为NULL时，它不再减去0，它减去null，因此新列返回INVOICED_QTY为空的空值

我尝试了多种方法：尝试合并到一个案例，将合并写为INVOICED然后在减法表达式中使用INVOICED，我尝试在同一行中使用coalesce作为减法（之间没有逗号，我觉得这是最好的解决方案，但无法编译）

Answer 1

您无法在ALIAS子句

上使用WHERE

SELECT  PICK_SO_NUMBER, 
        CUSTOMER, 
        SO_PRODUCT, 
        DO_QUANTITY, 
        DO_PACKING, 
        DO_DATE,
        COALESCE(INVOICED_QTY, 0) AS INVOICED_QTY, 
        DO_QUANTITY-INVOICED_QTY AS NOT_INVOICED, 
        INVOICE_PACKING 
FROM    VW_TRAFFIC_PO_SIDE
-- note that INVOICE_QTY in WHERE  DO_QUANTITY > INVOICED_QTY
-- does not compare the result of COALESCE(INVOICED_QTY, 0)
-- but to the original value of INVOICE_QTY
WHERE  DO_QUANTITY > COALESCE(INVOICED_QTY, 0) OR 
        (INVOICED_QTY IS NULL AND DO_QUANTITY IS NOT NULL)

原因如下：

FROM clause
WHERE子句
GROUP BY子句
HAVING条款
SELECT条款
ORDER BY子句

WHERE子句位于SELECT（，其中ALIAS的设置发生）子句之后。

但如果您真的想使用该别名，请将其包装在子查询中，例如

SELECT  *
FROM
(
    SELECT  PICK_SO_NUMBER, 
            CUSTOMER, 
            SO_PRODUCT, 
            DO_QUANTITY, 
            DO_PACKING, 
            DO_DATE,
            COALESCE(INVOICED_QTY, 0) AS INVOICED_QTY, 
            DO_QUANTITY-INVOICED_QTY AS NOT_INVOICED, 
            INVOICE_PACKING 
    FROM    VW_TRAFFIC_PO_SIDE
) s
WHERE    DO_QUANTITY > INVOICED_QTY OR 
        (INVOICED_QTY IS NULL AND DO_QUANTITY IS NOT NULL)

Answer 2

在select-list和WHERE子句中使用相同的别名'invoiced_qty'会让人感到困惑。减法中的值是原始列值，而不是前一个选择列表项的合并值。 WHERE子句也是如此。

SELECT PICK_SO_NUMBER, CUSTOMER, SO_PRODUCT, DO_QUANTITY, DO_PACKING, DO_DATE,
       COALESCE(INVOICED_QTY, 0) AS INVOICED_QTY, 
       DO_QUANTITY - COALESCE(INVOICED_QTY, 0) AS NOT_INVOICED, 
       INVOICE_PACKING 
  FROM VW_TRAFFIC_PO_SIDE
 WHERE DO_QUANTITY > INVOICED_QTY
    OR (INVOICED_QTY IS NULL AND DO_QUANTITY IS NOT NULL)

将空值设置为0，然后在运算符中使用0？

2 个答案: