爲什麼這個錯誤到來的Pos​​tgres

Question

我有一個下面的查詢

select wbod.subject, wbi.object, 
     age(dod.object,wbod.object) as ageOfPerson 
from wasbornin as wbi, 
    wasbornondate as wbod, 
    diedondate as dod 
where wbi.subject=wbod.subject 
    and wbod.subject=dod.subject 
    and age(dod.object,wbod.object) = (select max(age(dod1.object,wbod1.object)) 
            from wasbornin as wbi1, 
            wasbornondate as wbod1, 
            diedondate as dod1 
            where wbi1.subject = wbod1.subject 
            and wbod1.subject=dod1.subject 
            group by wbi1.object) 
group by wbi.object 
ORDER BY wbi.subject; 

但它給下面的錯誤

column "wbod.subject" must appear in the GROUP BY clause or be used in an aggregate function 
LINE 1: select wbod.subject, wbi.object 

這是爲什麼錯誤來

Answer 1

這是因爲您選擇此列。如果給定組（GROUP BY wbi.object），則有150個不同的主題，哪一個應該返回？

我最初誤讀了查詢 - 順序是使用wbi.subject，但錯誤是關於wbod.subject。

Answer 2

如果我正確理解您的查詢，你其實並不需要由子查詢或組：

select subject, 
     object, 
     ageOfPerson 
from (
    select wbod.subject, 
      wbi.object, 
      age(dod.object, wbod.object) as ageOfPerson, 
      dense_rank() over (partition by dod.subject order by age(dod.object, wbod.object) desc) as rnk 
    from wasbornin as wbi 
     join wasbornondate as wbod on wbi.subject=wbod.subject 
     join diedondate as dod on wbod.subject=dod.subject 
) t 
where rnk = 1;