查找具有相关最大日期行列匹配值的表的行吗？

哇这个问题真的很难简明扼要地制定。所以，这里的数据：查找具有相关最大日期行列匹配值的表的行吗？

Person: 
+----+---------+ 
| ID | Name | 
+----+---------+ 
| 1 | Bob  | 
| 2 | Alice | 
| 3 | Greg | 
| 4 | Lisa | 
+----+---------+ 

Activity: 
+----+----------+------------+----------+ 
| ID | PersonID | Date  | Activity | 
+----+----------+------------+----------+ 
| 1 | 1  | 2017-03-01 | foo  | 
| 2 | 1  | 2017-03-02 | bar  | 
| 3 | 2  | 2016-12-01 | foo  | 
| 4 | 3  | 2017-01-15 | foo  | 
+----+----------+------------+----------+

我想回到所有Person行，其最近期的Activity是foo。

Return: 
+----+---------+ 
| ID | Name | 
+----+---------+ 
| 2 | Alice | 
| 3 | Greg | 
+----+---------+

谢谢！

来源

2017-03-17 Rick

你尝试过什么？你使用哪个dbms？ – jarlh

我正在使用SQLite，但如果绝对必要，可以使用MySQL。我实际上是通过flask-sqlalchemy来做这件事的，我当然可以用代码来过滤它，但是我觉得SQL会更快。 – Rick

我试着修改这个答案，但无法让它工作得很正确：http://stackoverflow.com/questions/7745609/sql-select-only-rows-with-max-value-on-a-column – Rick

MySQL的

select P3.* 
from 
(
select PersonID, max(Date) as mDate 
from Activity 
group by PersonID 
) a1 
inner join Activity A2 
    on A2.PersonID = A1.PersonID 
    and A2.Date = A1.mDate 
inner join Person P3 
    on P3.ID = A2.PersonID 
where A2.Activity = 'Foo' 
and not exists (select 1 -- This is for those who did both on one day 
       from Activity A4 
       where A4.Activity = 'Bar' 
       and A4.PersonID = A1.PersonID 
       and A4.Date = A1.mDate)

和SQL服务器/甲骨文（乐趣）

with CTE as 
(
select A1.*, row_number() over(partition by PersonID order by Date desc) as r_ord 
from Activity A1 
) 
select P2.* 
from Person P2 
inner join CTE 
    on CTE.PersonID = P2.ID 
where CTE.r_ord = 1 
and CTE.Activity = 'Foo'

来源

2017-03-17 08:54:00 JohnHC

这似乎工作得很好，除了两个活动日期相同的情况。（未说明的）意图是找到“欺骗”但不“禁止”的人。我的数据有点肮脏，我可能只是把它清理干净。 – Rick

@Rick查看编辑 – JohnHC

select * from Person where ID in 
(select PersonID from (select Top 1 * from Activity where PersonID = Person.ID order by Activity.Date desc) Tmp where Tmp.Activity <> 'bar')

来源

2017-03-17 09:19:51

查找具有相关最大日期行列匹配值的表的行吗？

回答

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