mysql - 如何从 MySQL 中提取多列，其中一列是唯一值

Question

我有一个金发时刻，我有一个时间戳和值列，我想从 PHP MySQL 表“mytable”中查询。不过，我只想获取一个值以及该值的相应时间戳。例如:

value,timestamp
23,2016-09-01 00:04:05 
23,2016-09-01 00:04:05 
23,2016-09-02 01:04:05 < --- extract this
24,2016-09-02 01:05:13
24,2016-09-03 01:04:24 
27,2016-09-03 03:24:34 
27,2016-09-04 04:24:42
27,2016-09-05 05:54:12 
27,2016-09-06 00:04:05
27,2016-09-07 00:04:05 < --- extract this
28,2016-09-08 00:04:05 < --- extract this

我希望能够从上表中提取一个值及其相应的时间戳

value,timestamp
23,2016-09-02 01:04:05
27,2016-09-07 00:04:05
28,2016-09-08 00:04:05

问:查询会是什么样子？

Answer 1

试试这个

SELECT
    value,
    MAX(TIMESTAMP)
FROM
    yourTable
GROUP BY
    value