How to group by value, capturing the date of the last entry?

Question

MySQL

there is a table with time and current temperature
correspondences cm_stat(ID, DATETIME, CURTIME)
Query

SELECT `cm_stat`.`CURTEMP`, `cm_stat`.`DATETIME`
FROM `cm_stat`
ORDER BY `DATETIME` ASC

At the exit:

Array
(
    [CURTEMP] => 27
    [DATETIME] => 2017-09-22 13:47:41
)
Array
(
    [CURTEMP] => 26
    [DATETIME] => 2017-09-22 13:47:41
)
Array
(
    [CURTEMP] => 27
    [DATETIME] => 2017-09-22 13:48:41
)
Array
(
    [CURTEMP] => 27
    [DATETIME] => 2017-09-22 13:48:41
)
Array
(
    [CURTEMP] => 27
    [DATETIME] => 2017-09-22 13:49:41
)
Array
(
    [CURTEMP] => 27
    [DATETIME] => 2017-09-22 13:49:41
)
Array
(
    [CURTEMP] => 27
    [DATETIME] => 2017-09-22 13:50:41
)
Array
(
    [CURTEMP] => 26
    [DATETIME] => 2017-09-22 13:50:41
)

It is necessary to group by ranges, fixing the date of the last modification.
Result:

Array
(
    [CURTEMP] => 27
    [DATETIME] => 2017-09-22 13:47:41
)
Array
(
    [CURTEMP] => 26
    [DATETIME] => 2017-09-22 13:47:41
)
Array
(
    [CURTEMP] => 27
    [DATETIME] => 2017-09-22 13:50:41
)
Array
(
    [CURTEMP] => 26
    [DATETIME] => 2017-09-22 13:50:41
)

Answer 1

just group and sort by date (you already have sorting in your query)
in the grouping selection, the most extreme date will be shown, taking into account sorting.