SQL中刪除基於組由

Question

我有以下查詢：

select user_id, trajectory_id, count(trajectory_id) from point group by user_id, trajectory_id 

返回以下結果：

我想從point表中刪除，其中count中產生的表中的所有記錄是< 5 。

現在我有以下查詢，但它不是編譯。它有什麼問題，我該如何解決它？

delete 
from point 
where count(trajectory_id) < 5 
GROUP BY user_id, trajectory_id 

我正在使用Postgres。

Answer 1

delete p1 
from point p1 
join 
(
    select user_id, trajectory_id 
    from point 
    group by user_id, trajectory_id 
    having count(trajectory_id) < 5 
) p2 on p1.user_id = p2.user_id 
    and p1.trajectory_id = p2.trajectory_id 

Answer 2

我會用一個簡單的相關子查詢做到這一點：

delete from point 
    where (user_id, trajectory_id) in (select user_id, trajectory_id 
             from point 
             group by user_id, trajectory_id 
             having count(*) < 5 
            );