Question

你能告诉我如何在一组记录中选择最高的记录吗？例如，在下表中，我只想获取具有最新日期的记录（粗体）。

<头>

典型	序列	日期
A	1	1900-01-01
A	1	2002-01-06
A	1	2021-02-01
A	2	1900-01-01
A	2	2003-12-01
A	2	2004-12-05
A	2	2021-02-21
A	2	2021-01-06
A	3	2015-05-17
A	3	2017-11-26
A	3	2019-11-10
A	3	2021-01-01

非常感谢！

Answer 1

首先用group by SEQ 表，然后将表连接到同一个表并用 ROW_NUMBER() 创建行并按日期排序，然后在输出中显示结果行号为 1 的记录。

WITH resultTable AS (
SELECT 
RT.TYP,
RT.SEQ,
RT.DATE,   
ROW_NUMBER() OVER ( PARTITION BY RT.SEQ 
                         ORDER BY RT.DATE DESC ) AS [ROW NUMBER]
FROM MyTable RT
Inner JOIN 
(
  SELECT SEQ
  FROM MyTable
 GROUP BY SEQ
) LT ON RT.SEQ = LT.SEQ)
select resultTable.TYP,resultTable.SEQ,resultTable.DATE from resultTable
WHERE resultTable.[ROW NUMBER] = 1

Answer 2

一个简单的窗口函数应该可以做到：

select typ, seq, date
from (
  select typ, seq, date, 
         dense_rank() over (partition by typ, seq order by date desc) as rn
  from the_table
) t
where rn = 1
order by typ, seq;

选择组内最高记录

2 个答案: