我想从今天的最小值减去今天的最大值。我正确地获得了最大值,但最小值却变成了0。如何从kvarh的最大值中减去今天的最小值。
数据类型kvarh-浮动,devicetimestamp-日期时间
码
select(
SELECT MAX(kvarh)
FROM [Transformer].[dbo].[Total_Power]
WHERe DeviceTimeStamp < GETDATE()
and DEVICEIMEI = '868996')
-
(SELECT MIN(kvarh)
FROM [Transformer].[dbo].[Total_Power]
WHERe DeviceTimeStamp < GETDATE()
and DEVICEIMEI = '868996')
as Difference
样本数据
A_id DeviceImei DeviceTimeStamp KWH KVARH
985302 868996 2020-10-16 10:30:30.000 36682.5 424107.1
985298 868996 2020-10-16 10:15:31.000 36678.94 424103.3
985296 8689960 2020-10-16 10:00:29.000 36675.88 424099.8
我已经检查了您的查询,并且工作正常。您可以像这样减少一点:
DECLARE @DataSource TABLE
(
[A_id] INT
,[DeviceImei] INT
,[DeviceTimeStamp] DATETIME
,[KWH] DECIMAL(9,2)
,[KVARH] DECIMAL(9,2)
);
INSERT INTO @DataSource ([A_id], [DeviceImei], [DeviceTimeStamp], [KWH], [KVARH])
VALUES (985302, 868996, '2020-10-16 00:30:30.000', 36682.5, 424107.1)
,(985298, 868996, '2020-10-16 00:15:31.000', 36678.94, 424103.3)
,(985296, 8689960, '2020-10-16 00:00:29.000', 36675.88, 424099.8);
SELECT MAX(kvarh) - MIN(kvarh) AS Difference
FROM @DataSource
WHERE DeviceTimeStamp < GETDATE()
and DEVICEIMEI = '868996';
该MIN
函数将不返回0
此示例数据-如果未找到任何行,您将得到NULL
结果。0
仅当只有一行符合您的条件时,您才会得到,因为您将减去相同的值。
例如:
DECLARE @DataSource TABLE
(
[A_id] INT
,[DeviceImei] INT
,[DeviceTimeStamp] DATETIME
,[KWH] DECIMAL(9,2)
,[KVARH] DECIMAL(9,2)
);
INSERT INTO @DataSource ([A_id], [DeviceImei], [DeviceTimeStamp], [KWH], [KVARH])
VALUES (985302, 868996, '2020-10-16 00:30:30.000', 36682.5, 424107.1)
--,(985298, 868996, '2020-10-16 00:15:31.000', 36678.94, 424103.3)
,(985296, 8689960, '2020-10-16 00:00:29.000', 36675.88, 424099.8);
SELECT MAX(kvarh) - MIN(kvarh) AS Difference
FROM @DataSource
WHERE DeviceTimeStamp < GETDATE()
and DEVICEIMEI = '868996';
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