Question

我正在使用MSSQL 2008 R2，并遇到以下情况的问题：

通过以下查询，我将获得我期望的数据（每个日期的max和min速度。 CAST(m.date as DATE)删除了datetime

的时间部分

SELECT CAST(d.date as DATE) as date,
       MAX(d.speed) AS maxSpeed,
       AVG(d.speed) AS avgSpeed
  FROM Driver as d
 WHERE d.date between '2014-01-01 09:00:00.491' and
       '2014-03-11 17:00:00.491'
 GROUP BY CAST(d.date as DATE)
 ORDER BY date DESC

我的问题是，我想从d中选择一些其他字段（如userID，username等）。如果我修改查询以包含其他字段，如下所示：

SELECT CAST(d.date as DATE) as date,
       MAX(d.speed) AS maxSpeed,
       AVG(d.speed) AS avgSpeed,
       d.userId
  FROM Driver as d
 WHERE d.date between '2014-01-01 09:00:00.491' and
       '2014-03-11 17:00:00.491'
 GROUP BY CAST(d.date as DATE)
 ORDER BY date DESC

我收到此错误：

d.userId is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

因此，我将d.userId添加到GROUP BY子句中，当然，我的数据会发生变化，现在每个日期会包含多个条目。

所以，我的问题是如何选择其他字段，同时仍保留我想要的原始数据（每个唯一日期min和max）？

Answer 1

如果您要从Driver中选择行以及max()的{{1}}和avg()值，请使用窗口函数：

speed

编辑：

如果您希望每个驱动程序每行一行，请使用简单的SELECT d.*, CAST(d.date as DATE) as date, MAX(d.speed) OVER (PARTITION BY CAST(d.date as DATE)) AS maxSpeed, AVG(d.speed) OVER (PARTITION BY CAST(d.date as date)) AS avgSpeed FROM Driver as d WHERE d.date between '2014-01-01 09:00:00.491' and '2014-03-11 17:00:00.491' ORDER BY date DESC;：

group by

如果您想添加其他列，则需要将它们添加到SELECT d.userId, CAST(d.date as DATE) as date, MAX(d.speed) as maxSpeed, AVG(d.speed) as avgSpeed FROM Driver as d WHERE d.date between '2014-01-01 09:00:00.491' and '2014-03-11 17:00:00.491' GROUP BY d.userId, CAST(d.date as DATE) ORDER BY date DESC;和select。

使用GROUP BY时选择其他字段

1 个答案: