Question

我有两个表：

操作（op_id，super，name，last）订单（或编号，数量）

操作：

+--------------------------------+
|op_id| super| name        | last|
+--------------------------------+
|1       1      OperationXX    1 |
|2       1      OperationXY    2 |
|3       1      OperationXC    4 |
|4       1      OperationXZ    3 |
|5       2      OperationXX    1 |
|6       3      OperationXY    2 |
|7       4      OperationXC    1 |
|8       4      OperationXZ    2 |
+--------------------------------+

订单：

+--------------+
|or_id | number|
+--------------+
|1        2UY  |
|2        23X  |
|3        xx2  |
|4        121  |
+--------------+

我需要查询才能获取表：

+-------------------------------------+
|or_id |number |max(last)|   name     |
|1      2UY     4          OperationXC|    
|2      23X     1          OperationXX|    
|3      xx2     2          OperationXY|    
|4      121     2          OperationXZ|    
+-------------------------------------+

Answer 1

使用corelared子查询并加入

select o.*,a.last,a.name from
(
select super,name,last from Operations  from operations t
 where last = (select max(last) from operations t2 where t2.super=t.super)

) a join orders o on t1.super =o.or_id

您也可以使用row_number

with cte as

(
select * from 
(
select * , row_number() over(partition by super order by last desc) rn
from operations
) tt where rn=1

) select o.*,cte.last,cte.name from Orders o join cte on o.or_id=cte.super

Answer 2

    SELECT Orders.or_id, Orders.number, Operations.name, Operations.last AS max
    FROM Orders
    INNER JOIN Operations on Operations.super = Orders.or_id
    GROUP BY Orders.or_id, Orders.number, Operations.name;

我目前无法测试此方法，但我认为就是这样。

此外，您没有指定外键，因此联接可能是错误的。

联接表的最大值

2 个答案: