获取两个日期之间的最小值和最大值

Question

我正在查询以下代码，以获取min，max和avg，但是仍然给我一个问题，因为它查询了name = 'Jose'中我所拥有的所有行，而不是min，max和avg。

SELECT CONVERT(CHAR(10), DATA, 120) AS DATA, 
MIN([VALUE]) AS MinValue, 
AVG([VALUE]) AS MedValue, 
MAX([VALUE]) AS MaxValue
FROM databasename
WHERE (name = 'Jose')
GROUP BY CONVERT(CHAR(10), DATA, 120)
ORDER BY DATA ASC

从第一个查询中得到的示例： Image（无法嵌入图片）

要查询两个日期，我正在使用以下代码，但查询没有任何结果。

SELECT CONVERT(CHAR(10), DATA, 120) AS DATA, 
MIN([VALUE]) AS MinValue, 
AVG([VALUE]) AS MedValue, 
MAX([VALUE]) AS MaxValue
FROM databasename
WHERE [DATA] between '2017-02-01' AND '2018-03-10' AND name = 'Jose'
GROUP BY CONVERT(CHAR(10), DATA, 120)
ORDER BY DATA ASC

我正在使用MSSQL数据库。

更新： 正如您在第二个查询中看到的那样，我已经可以在两个日期之间进行查询。问题是我不能只获得最小值，最大值和平均值。 图片：

Answer 1

如果DATA是DATE字段？
然后将这些日期字符串转换为DATE，而不是转换为VARCHAR。

SELECT -- DATA AS DATA, 
MIN([VALUE]) AS MinValue, 
AVG([VALUE]) AS MedValue, 
MAX([VALUE]) AS MaxValue
FROM databasename
WHERE [DATA] between CONVERT(DATE, '2017-02-20') AND CONVERT(DATE, '2018-02-25') 
  AND name = 'Jose'
-- GROUP BY DATA
-- ORDER BY DATA ASC

如果DATA是varchar，那么CONVERT或CAST也会在WHERE子句中执行DATE。

如果只需要1行作为结果，则可以删除select中的GROUP BY，ORDER BY和DATA。

如果DATA是DATETIME，则CAST或CONVERT也将有所帮助。
例如，参见此测试代码段

declare @DT DATETIME = '2018-01-02 12:15:30';

select 
  IIF(CAST(@DT AS DATE) BETWEEN '2018-01-01' AND '2018-01-02','Yes','No') AS DT_AS_DATE_IS_BETWEEN_DATES
, IIF(@DT BETWEEN '2018-01-01' AND '2018-01-02','Yes','No') AS DT_AS_DATETIME_IS_BETWEEN_DATES;
-- returns the tupple ('Yes' ,'No')

Answer 2

尝试执行此SQL查询Convert（DATE，'2017-02-01'）。

SELECT DATA AS DATA, 
MIN([VALUE]) AS MinValue, 
AVG([VALUE]) AS MedValue, 
MAX([VALUE]) AS MaxValue
FROM databasename
WHERE [DATA] between CONVERT(DATE, '2017-02-01') AND CONVERT(DATE, '2018-03-10') 
  AND name = 'Jose'
GROUP BY CONVERT(DATE, '2017-02-20')
ORDER BY CONVERT(DATE, '2017-02-20') ASC

Answer 3

您可以考虑在查询中进行小的更改

SELECT CONVERT(CHAR(10), DATA, 120) AS DATA,
MIN([VALUE]) AS MinValue,
AVG([VALUE]) AS MedValue,
MAX([VALUE]) AS MaxValue
FROM databasename
WHERE CONVERT(CHAR(10), DATA, 120) between CONVERT(CHAR(10), 2017 - 02 - 20, 120) AND
CONVERT(CHAR(10), 2018 - 02 - 25, 120) AND name = 'Jose'
GROUP BY CONVERT(CHAR(10), DATA, 120)
ORDER BY DATA ASC