获取最近标记的记录

Question

我有以下 MySQL (v5.7) table:

ID	PersonID	Featured	CreatedAt
1743455	54924	0	2021-10-21 12:15:54
1743460	54924	1	2021-10-21 12:30:38
1743465	54924	0	2021-10-21 12:52:05
1743467	54924	0	2021-10-21 12:54:58
1743471	54924	0	2021-10-21 13:10:22
1743472	54924	1	2021-10-21 13:23:27
1743473	54924	0	2021-10-21 13:42:00
1743474	54924	0	2021-10-21 13:43:50
1743475	54924	0	2021-10-21 13:47:08
1743476	54924	0	2021-10-21 13:48:36
1743484	54924	1	2021-10-21 16:31:03

我想要一个查询来创建一个标记最新特写照片的列

预期结果：

ID	PersonID	Featured	CreatedAt	MostRecentFeatured
1743455	54924	0	2021-10-21 12:15:54	0
1743460	54924	1	2021-10-21 12:30:38	0
1743465	54924	0	2021-10-21 12:52:05	0
1743467	54924	0	2021-10-21 12:54:58	0
1743471	54924	0	2021-10-21 13:10:22	0
1743472	54924	1	2021-10-21 13:23:27	0
1743473	54924	0	2021-10-21 13:42:00	0
1743474	54924	0	2021-10-21 13:43:50	0
1743475	54924	0	2021-10-21 13:47:08	0
1743476	54924	0	2021-10-21 13:48:36	0
1743484	54924	1	2021-10-21 16:31:03	1

我该怎么做？

我尝试使用子查询，但它减慢了我的查询速度。

Answer 1

在 mysql 8+ :

select * , case when row_number() over (partition by PersonId order by CreatedAt desc) = 1 then 1 else 0 end as MostRecentFeatured
from table1

年长 mysql :

select a.*, case when b.personId is not null then 1 else 0 end as mostrecent
from table a
left join (
    select PersonId, max(CreatedAt) as CreatedAt
    from table
    group by PersonId
) b on a.CreatedAt = b.CreatedAt
    and a.PersonId = b.PersonId

获取最近标记的记录

Get most recent flagged record

mysql

sql

mysql-5.7