查找具有相關最大日期行列匹配值的表的行嗎？

哇這個問題真的很難簡明扼要地制定。所以，這裏的數據：查找具有相關最大日期行列匹配值的表的行嗎？

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 | 
+----+---------+

謝謝！

來源

2017-03-17 Rick

你嘗試過什麼？你使用哪個dbms？ – jarlh

我正在使用SQLite，但如果絕對必要，可以使用MySQL。我實際上是通過flask-sqlalchemy來做這件事的，我當然可以用代碼來過濾它，但是我覺得SQL會更快。 – Rick

我試着修改這個答案，但無法讓它工作得很正確：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服務器/甲骨文（樂趣）

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'

來源

2017-03-17 08:54:00 JohnHC

這似乎工作得很好，除了兩個活動日期相同的情況。（未說明的）意圖是找到「欺騙」但不「禁止」的人。我的數據有點骯髒，我可能只是把它清理乾淨。 – Rick

@Rick查看編輯 – 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')

來源

2017-03-17 09:19:51

查找具有相關最大日期行列匹配值的表的行嗎？

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