Select 只查询 return 没有分组依据的最小日期时间？

Question

我的table显示如下，

|_______________|____________|_____________________|______________________|
|  ENTRY POINT  |    NAME    |    DATE OF ENTRY    |   DATETIME OF ENTRY  | 
|_______________|____________|_____________________|______________________|
|    CHECKIN    |  CHOCOTACO |     05/07/2018      | 05/07/2018 00:01:00  | 
|_______________|____________|_____________________|______________________|
|    CHECKIN 1  |  CHOCOTACO |     05/07/2018      | 05/07/2018 00:01:10  | 
|_______________|____________|_____________________|______________________|
|    CHECKIN 2  |  CHOCOTACO |     05/07/2018      | 05/07/2018 00:01:15  | 
|_______________|____________|_____________________|______________________|
|    CHECKIN 10 |  CHOCOTACO |     06/07/2018      | 06/07/2018 00:07:10  | 
|_______________|____________|_____________________|______________________|
|    CHECKIN 4  |  CHOCOTACO |     06/07/2018      | 06/07/2018 00:07:10  | 
|_______________|____________|_____________________|______________________|
|    CHECKIN 5  |  CHOCOTACO |     06/07/2018      | 06/07/2018 00:09:15  | 
|_______________|____________|_____________________|______________________|

预期输出只是第一个值，它具有如下每天的最小输入日期时间，

|_______________|____________|_____________________|______________________|
|  ENTRY POINT  |    NAME    |    DATE OF ENTRY    |   DATETIME OF ENTRY  | 
|_______________|____________|_____________________|______________________|
|    CHECKIN    |  CHOCOTACO |     05/07/2018      | 05/07/2018 00:01:00  | 
|_______________|____________|_____________________|______________________|
|    CHECKIN 10 |  CHOCOTACO |     06/07/2018      | 06/07/2018 00:07:10  | 
|_______________|____________|_____________________|______________________|

如果我尝试使用最短的进入日期时间，它可能会让我使用 group by 'ENTRY POINT' 和其他列，这些列基本上给我的输出与我的输入相同。

请帮我解决这个问题。

Answer 1

您可以使用window函数row_number()。这是 demo.

select
    ENTRY_POINT,   
    NAME, 
    DATE_OF_ENTRY,   
    DATETIME_OF_ENTRY
from    
(
    select
        *,
        row_number() over (order by DATETIME_OF_ENTRY) as rnk
    from myTable
) t
where rnk = 1

Answer 2

您需要 window 个分析函数，其中 DENSE_RANK() 很适合包含所有关系（每个 [=13] 具有相同 [DATETIME OF ENTRY] 值的记录=] 和 [DATE OF ENTRY] 组合 )。

需要找出按每个 [NAME] 和 [DATE OF ENTRY] 分组（分区）的升序 [DATETIME OF ENTRY] 值的第一个记录：

SELECT [ENTRY POINT], [NAME], [DATE OF ENTRY], [DATETIME OF ENTRY]
  FROM
 (
  SELECT T.*,
         DENSE_RANK() OVER 
              (PARTITION BY [NAME], [DATE OF ENTRY] ORDER BY [DATETIME OF ENTRY]) AS dr
    FROM T -- <your table>
  ) TT
  WHERE dr = 1;

Select 只查询 return 没有分组依据的最小日期时间？

Select query to return only the min datetime without group by?

sql

sql-server

sqldatetime