获取给定ID的最新行 [英] Get most recent row for given ID
本文介绍了获取给定ID的最新行的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
在下表中,如何根据 signin
列仅获取最近行和 id = 1
全部三行?
In the table below, how do I get just the most recent row with id=1
based on the signin
column, and not all 3 rows?
+----+---------------------+---------+
| id | signin | signout |
+----+---------------------+---------+
| 1 | 2011-12-12 09:27:24 | NULL |
| 1 | 2011-12-13 09:27:31 | NULL |
| 1 | 2011-12-14 09:27:34 | NULL |
| 2 | 2011-12-14 09:28:21 | NULL |
+----+---------------------+---------+
推荐答案
使用按ID分组的汇总 MAX(signin)
.这将列出每个 id
的最新登录
.
Use the aggregate MAX(signin)
grouped by id. This will list the most recent signin
for each id
.
SELECT
id,
MAX(signin) AS most_recent_signin
FROM tbl
GROUP BY id
要获取完整的单个记录,请对子查询执行 INNER JOIN
,该子查询仅返回每个ID的 MAX(signin)
.
To get the whole single record, perform an INNER JOIN
against a subquery which returns only the MAX(signin)
per id.
SELECT
tbl.id,
signin,
signout
FROM tbl
INNER JOIN (
SELECT id, MAX(signin) AS maxsign FROM tbl GROUP BY id
) ms ON tbl.id = ms.id AND signin = maxsign
WHERE tbl.id=1
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