A

ID | B_ID
--- | ------
1 | 1
1 | 4
2 | 3
2 | 2
----------

乙

B_ID | B_VA | B_VB
------- | -------- | -------
1 | 1 |一个
2 | 2 | b
3 | 5 | ç
4 | 2 | d
-----------------------

从这两个表中我需要A.ID，B.B_ID，B.B_VA（MAX），B.B_VB（最大B.B_VA）所以结果表就像

ID | B_ID | B_VA | B_VB
------- | -------- | -------- | -------
1 | 4 | 2 | d
2 | 3 | 5 | Ç

我尝试了一些没有成功的连接。任何人都可以帮我查询以获得我想要的结果。

谢谢

Answer 1

您描述的逻辑与数据不完全对应。例如，b_va是数字，但输出中的列是字符串。

也许你想要这个。要汇总a中的数据以获取最大b_id值。然后，每个要连接的列将获得相应的b_vb列。这至少符合你想要的输出：

select a.id, a.b_id, b1.b_vb as b_va, b2.b_vb
from (select id, max(b_id) as b_id
      from a
      group by id
     ) a join
     b b1
     on a.id = b1.b_id join
     b b2
     on a.b_id = b2.b_id;

编辑：

对于更正后的数据，我认为这就是您想要的：

select a.id, a.b_id, max(b1.b_va) as b_va, b2.b_vb
from (select id, max(b_id) as b_id
      from a
      group by id
     ) a join
     b b1
     on a.id = b1.b_id join
     b b2
     on a.b_id = b2.b_id
group by a.id, a.b_id, b2.b_vb;

Answer 2

试试这个

SELECT X.ID, Y.B_ID, X.B_VA, Y.B_VB
  FROM (SELECT A.ID, MAX(B_VA) AS B_VA
          FROM A INNER JOIN B ON A.B_ID = B.B_ID 
          GROUP BY A.ID) AS X INNER JOIN
       A AS Z ON X.ID = Z.ID INNER JOIN
       B AS Y ON Z.B_ID=Y.B_ID AND X.B_VA=Y.B_VA

SQL连接从右表获取具有最大值的行

A

乙

2 个答案: