排序依据和分组依据

Question

是否有一种有效的方法来执行排序依据和分组依据，以便您从每个组（从排序依据）中获取特定的项目。

//This is the best way i have come up with.
SELECT D.*
FROM (
    SELECT *
    FROM devices
    ORDER BY time
) AS D
GROUP BY D.location

Answer 1

这对我有用

SELECT *
FROM (SELECT *
      FROM col
      ORDER BY col DESC,date DESC)a
GROUP BY col

Answer 2

SELECT *
FROM devices
GROUP BY D.location
ORDER BY time --ASC or DESC default is ASC i believe

不需要子查询