Question

我有3张表，比如

A. (Aid,person)

B. (Bid,event,InsertDate)

C. (Cid,Aid,Bid)

现在我需要在加入B.InsertDate和B.event的{{1}} desc上获取最近的最新活动基数（每个人的最后一次活动）我尝试了加入，但这会产生多个A.Person和A.Person。你能指导我吗？

更新

现在我只是将另一个lastUpdate列添加到person表中，并为Event表中的每个插入更新，并使其等于InsertDate。所以我的查询就像：

B.event

Answer 1

试试这个：

SELECT
  A.person,
  B.event,
  MAX(B.InsertDate)
FROM
  A
  JOIN C ON A.Aid = C.Aid
  JOIN B ON B.Bid = C.Bid
GROUP BY
  A.person,
  B.event

Answer 2

可能是这样的

WITH cte
     AS (SELECT Row_number() OVER (partition BY person ORDER BY B.InsertDate DESC) rn,
                A.person,
                B.event,
                B.InsertDate                    AS LastEventDate
         FROM   B
                JOIN (SELECT B.event,
                             Max(B.InsertDate) InsertDate
                      FROM   B
                      GROUP  BY B.event) sub
                  ON sub.event = B.event
                     AND sub.InsertDate = b.InsertDate
                JOIN A
                  ON A.Bid = C.Bid
                JOIN C
                  ON B.Bid = C.Bid)
SELECT *
FROM   cte
WHERE  rn = 1

SQL，刚刚从多对多关系中获取（在一行中）

2 个答案: