Question

我有一个金发碧眼的时刻，我有一个时间戳和值列，我想从PHP MySQL表“mytable”查询。但是我想只获得一个值和对应的时间戳作为一个值。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value并且相应的timestamp

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

问：查询会是什么样的？

Answer 1

试试这个

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

如何提取多个列，一个是MySQL的唯一值

1 个答案: