[英]MySql Group By and order by date
這是我的表數據:
id page_id time created
=======================================================
1 1 00:15:00 2020-11-05 09:55:54
2 1 00:25:00 2020-11-10 07:35:24
3 2 00:10:25 2020-11-06 06:15:20
這是 MySql 查詢:
SELECT
a.* SUM (a.time) AS time
FROM
`activity` AS a
GROUP BY a.page_id
ORDER BY a.created DESC;
期望的結果是將最新的記錄顯示在頂部,但相反,我將第一條記錄顯示在頂部;
喜歡:
2 1 00:25:00 2020-11-10 07:35:24
3 2 00:10:25 2020-11-06 06:15:20
相反,我得到了這個:
1 1 00:15:00 2020-11-05 09:55:54
3 2 00:10:25 2020-11-06 06:15:20
您似乎想要每個id
的最新記錄,如created
所定義。 如果是這樣,您需要過濾而不是聚合。
在 MySQL 8.0 中,我建議使用窗口函數:
select *
from (
select a.*,
rank() over(partition by page_id order by created desc) rn
from activity a
) a
where rn = 1
order by created desc
在早期版本中,您可以使用相關子查詢進行過濾:
select a.*
from activity a
where a.created = (
select max(a1.created) from activity a1 where a1.page_id = a.page_id
)
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