Question

我有这个查询

SELECT (SELECT cost FROM table1 t2 WHERE t2.edate=>table1.edate) AS cost
FROM table1
WHERE table1.orderNo = 'CS119484568'

以上查询返回：

cost
4
3
null
null
5

我想获取全部的总和，或者如果任何行为空，则为空

SELECT SUM((SELECT cost FROM table1 t2 WHERE t2.edate=>table1.edate)) AS cost
FROM table1
WHERE table1.orderNo = 'CS119484568'

在上述情况下，预期结果为NULL。

Answer 1

这是我的尝试：

SELECT
    (SELECT
        case when count(*)=count(cost) then sum(cost) else null end
     FROM table1 t2
     WHERE t2.edate=>table1.edate
    ) AS cost
FROM table1
WHERE table1.orderNo = 'CS119484568'

这是基于count()仅计算非空值的事实。

Answer 2

您可以使用if

SELECT IF((SELECT COUNT(*) FROM table1 t2 WHERE t2.edate=>table1.edate AND cost IS NULL), null, (SELECT SUM(cost) FROM table1 t2 WHERE t2.edate=>table1.edate)) AS cost FROM table1 WHERE table1.orderNo = 'CS119484568'

Answer 3

我想我的查询短语为：

SELECT SUM(CASE WHEN t1.edate >= tt1.edate THEN cost END)
FROM table1 t1 CROSS JOIN
     (SELECT edate
      FROM table1
      WHERE t1.orderNo = 'CS119484568'
     ) tt1;

然后我将使用CASE表达式作为结果：

SELECT (CASE WHEN SUM(t1.edate >= tt1.edate AND cost IS NOT NULL) = 0  -- no nulls
             THEN SUM(CASE WHEN t1.edate >= tt1.edate THEN cost END)
        END)
FROM table1 t1 CROSS JOIN
     (SELECT edate
      FROM table1
      WHERE t1.orderNo = 'CS119484568'
     ) tt1;

SUM函数，如果存在空值则返回空

3 个答案: