Question

我有两列需要基于WHERE语句进行求和，然后每列返回一个总计，并且我还需要将所得的SUM值加起来以得出最终的总计。

我可以使用UNION ALL获取每列的单个SUM值，但是无法将它们加起来成为最终的总数。

SELECT ISNULL(SUM(NILH1), 0) AS SUM
FROM [IG_300M19].[dbo].[Stn14_RFT]
WHERE NILH1 <= 25
  AND DateStamp BETWEEN '2019-03-17 08:00' AND '2019-04-17 08:00'

UNION ALL

SELECT ISNULL(SUM(NILH2), 0) AS SUM
FROM [IG_300M19].[dbo].[Stn14_RFT]
WHERE NILH2 <= 25
  AND DateStamp BETWEEN '2019-03-17 08:00' AND '2019-04-17 08:00';

上面返回两个值，一个对NILH1总计，一个对NILH2，现在我需要将它们加在一起得出最终的总数。

Answer 1

考虑到两个查询具有相同的WHERE，这不是那么简单：

SELECT SUM(ISNULL(CASE WHEN NILH1 <= 25 THEN NILH1 END, 0)) AS NILH1SUM,
       SUM(ISNULL(CASE WHEN NILH2 <= 25 THEN NILH2 END, 0)) AS NILH2SUM,
       SUM(ISNULL(CASE WHEN NILH1 <= 25 THEN NILH1 END, 0) + ISNULL(CASE WHEN NILH2 <= 25 THEN NILH2 END, 0)) AS TotalSum
FROM [IG_300M19].[dbo].[Stn14_RFT]
WHERE DateStamp BETWEEN '2019-03-17 08:00' AND '2019-04-17 08:00';

要对一列执行SUM，则不需要多个SELECT语句，您可以在同一条语句中的多个列上进行汇总，并可以使用这些表达式进行进一步的计算。

Answer 2

使用条件聚合；将条件从WHERE子句移至SUM函数：

SELECT SUM(
    CASE WHEN NILH1 <= 25 THEN NILH1 ELSE 0 END +
    CASE WHEN NILH2 <= 25 THEN NILH2 ELSE 0 END
)
FROM [IG_300M19].[dbo].[Stn14_RFT]
WHERE DateStamp BETWEEN '2019-03-17 08:00' AND '2019-04-17 08:00'

Answer 3

对于这样的示例数据：

select * into #tab from (
    select 1 as NILH1,  2 as NILH2, cast('2019-03-17 18:00' as datetime) as DateStamp
    union all select 2, 3, cast('2019-03-17 18:00' as datetime)
    union all select 3, 4, cast('2019-03-17 18:00' as datetime)
    union all select 4, 5, cast('2019-06-17 18:00' as datetime)
    union all select 28, 29, cast('2019-03-17 18:00' as datetime)
) data

select * from #tab

--  NILH1   NILH2  DateStamp
--  --------------------------------------
--  1       2      2019-03-17 18:00:00.000
--  2       3      2019-03-17 18:00:00.000
--  3       44     2019-03-17 18:00:00.000  
--  4       5      2019-06-17 18:00:00.000  <-- invalid timestamp
--  28      6      2019-03-17 18:00:00.000

您可以使用CTE：

;with SUMS as
(
    SELECT
        SUM(CASE WHEN NILH1 <= 25 THEN NILH1 ELSE 0 END) as NILH1SUM,
        SUM(CASE WHEN NILH2 <= 25 THEN NILH2 ELSE 0 END) as NILH2SUM
    FROM #tab
    WHERE DateStamp BETWEEN '2019-03-17 08:00' AND '2019-04-17 08:00'
)
select
    NILH1SUM as NILH1SUM,
    NILH2SUM as NILH2SUM,
    NILH1SUM + NILH2SUM as TOTAL
from
    SUMS

-- NILH1SUM NILH2SUM TOTAL
-- -----------------------
-- 6        11        17

如何获得多个SUM语句的总计

3 个答案: