MySQL:获取最新记录
问题描述：
在下表中，如何仅根据登录列获取
In the table below, how do I get just the most recent record of id=1 based on the signin column and not all 3 records?
+----+---------------------+---------+
| 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 |
+----+---------------------+---------+
答
使用按ID分组的汇总MAX(signin).这将列出每个id的最新signin.
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
要获取整个单个记录，请对子查询执行INNER JOIN，该子查询仅返回每个id 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