sql - 如何在 T-SQL 中打印最新的一行？

Question

-----------------------------------------------
Value     ISRepeat    Changed
------------------------------------------------
666-66-8888 NULL    2011-10-19 15:28:47.310
555-55-6666 NULL    2011-10-19 15:27:26.413
444-44-5555 NULL    2011-10-19 15:25:02.660
333-33-4444 NULL    2011-10-19 15:23:57.120
222-22-3333 NULL    2011-10-19 15:13:57.903
222-22-2222 NULL    2011-10-19 15:13:03.517
100-10-2222 NULL    2011-10-19 15:07:52.010
100-10-1111 NULL    2011-10-19 15:06:59.690

我有一张这样的 table 。我想打印该值

555-55-6666 NULL    2011-10-19 15:27:26.413

这是表中基于时间(更改列)的最后一行...条件是最近值之前的时间。我怎样才能做到这一点？

Answer 1

最近时间是通过以下方式找到的:

SELECT MAX(Changed) AS most_recent FROM AnonymousTable

您希望最大时间小于此的行:

SELECT MAX(Changed) AS second_latest
  FROM AnonymousTable
 WHERE Changed < (SELECT MAX(Changed) AS most_recent FROM AnonymousTable)

因此，您选择相关行:

SELECT *
  FROM AnonymousTable
 WHERE Changed =
       (SELECT MAX(Changed) AS second_latest
          FROM AnonymousTable
         WHERE Changed < (SELECT MAX(Changed) AS most_recent FROM AnonymousTable)
       )

可能有一种更简洁的方法来做到这一点，但这种技术不能很好地推广到第三或第四个最新值。 OLAP 功能很可能会有所帮助。