Question

考虑这个24小时的摘要。问题是，我已经在0小时内返回0，但尚未插入值。我认为这是由于 SUM() 函数调用。

SELECT
    section,
    [21], [22], [23], [0], [1], [2], [3], [4], [5], [6], [7], [8],
    [21] + [22] + [23] + [0] + [1] + [2] + [3] + [4] + [5] + [6] + [7] + [8] as s1_total
    -- shift 2 fields are ommitted for brievity
FROM (
    SELECT 
        section,
        -- hours from 21:00 (1st shift) to 20:00 (2nd shift)
        SUM(CASE WHEN prTime = '21:00:00' THEN Amount ELSE 0 END) AS [21],
        SUM(CASE WHEN prTime = '22:00:00' THEN Amount ELSE 0 END) AS [22],
        SUM(CASE WHEN prTime = '23:00:00' THEN Amount ELSE 0 END) AS [23],
        SUM(CASE WHEN prTime = '00:00:00' THEN Amount ELSE 0 END) AS [0],
        SUM(CASE WHEN prTime = '01:00:00' THEN Amount ELSE 0 END) AS [1],
        SUM(CASE WHEN prTime = '02:00:00' THEN Amount ELSE 0 END) AS [2],           
        -- ... similar cases are omitted for brieviety
        SUM(CASE WHEN prTime = '20:00:00' THEN Amount ELSE 0 END) AS [20]
    FROM (
        SELECT prTime, prDate, section01 AS Amount, 'section 1' as [Section] FROM SectionsHourlyValues
        UNION
        SELECT prTime, prDate, section02 AS Amount, 'section 2' as [Section] FROM SectionsHourlyValues
        UNION
        SELECT prTime, prDate, section03 AS Amount, 'section 3' as [Section] FROM SectionsHourlyValues
    ) AS U
    WHERE 
        (prDate = CONVERT(DATE, DATEADD(HOUR, -4, CONVERT(DATETIME2(7), @dt, 104))) and prTime > '20:00:00') or 
        (prDate = CONVERT(DATE, @dt, 104) and prTime <= '20:00:00')
    GROUP BY section
) t;

例如，运行查询

DECLARE @dt varchar(10) = 'certain_date';
SELECT * from [dbo].[SectionsHourlyValues] WHERE
    (prDate = CONVERT(DATE, DATEADD(HOUR, -4, CONVERT(DATETIME2(7), @dt, 104))) and prTime > '20:00:00') or 
    (prDate = CONVERT(DATE, @dt, 104) and prTime <= '20:00:00');

不会向我们返回说明 09:00:00 / section1 的数据，而摘要会向我们显示 0 。

然后我想显示 NULL （对于尚未插入的记录），而不是 0 。我该怎么做？

Answer 1

使用NULLIF

离

NULLIF(SUM(CASE WHEN prTime = '21:00:00' THEN Amount ELSE 0 END),0)

或者根本不使用ELSE

SUM(CASE WHEN prTime = '21:00:00' THEN Amount END)

Answer 2

如何在条件聚合中用NULL替换0？

SUM(CASE WHEN etc... ELSE NULL END)

Answer 3

你得到的0值不是由于SUM函数尚未插入的值（这将是NULL并且会被SUM函数忽略），而是因为你的CASE语句的ELSE返回0：

SUM(CASE WHEN prTime = '21:00:00' THEN Amount ELSE 0 END) AS [21]

要解决您的问题，您可以使用与NULLIF非常相似的CASE：

NULLIF(MyExpressionThatCouldReturn0, 0)

在你的情况下，那将是：

NULLIF(SUM(CASE WHEN prTime = '01:00:00' THEN Amount ELSE 0 END),0)

否则，如前所述，不要在CASE语句中使用ELSE，用作SUM的参数：

SUM(CASE WHEN prTime = '21:00:00' THEN Amount END)

使用sum aggregate / pivoting

3 个答案: