mysql - MySQL：按组内排序

Question

我有一个这样的mysql表：

mysql> select * from pt_onhand where pn = '000A569011';
+------------+-----+----+--------+------------+---------+--------------+-----+
| pn         | pa  | mn | ACTIVE | locate     | onhand  | avg_cost     | whs |
+------------+-----+----+--------+------------+---------+--------------+-----+
| 000A569011 | P/A |    |        | AA-112     | 13.0000 | 0.0000000000|     |
| 000A569011 | P/A |    |        | PF120136.1 |  1.0000 | 5.4785156200 |     |
+------------+-----+----+--------+------------+---------+--------------+-----+

我想执行这样的查询：

mysql> select sum(onhand),max(locate),avg_cost from pt_onhand where pn = '000A569011' group by pn;
+-------------+-------------+--------------+
| sum(onhand) | max(locate) | avg_cost     |
+-------------+-------------+--------------+
|     14.0000 | PF120136.1  | 0.0000000000|
+-------------+-------------+--------------+

所以我的问题是：我能否在同一个查询中获得与 max(locate) PF120136.1 相关的 avg_cost 5.4785156200，如何？谢谢

Answer 1

这有点杂乱无章，但它应该可以解决问题：

select a.onhand, a.locate, p.avg_cost
from
    (select sum(onhand) onhand, max(locate) locate from pt_onhand where pn = '000A569011' group by pn) a
    join pt_onhand p on p.locate = a.locate

Answer 2

你也可以做一个子查询：

select 
     sum(onhand)
    ,max(locate)
    ,(select avg_cost from pt_onhand where pn = pt.pn and locate = max(pt.locate)) as avg_cost 
from 
    pt_onhand pt 
where 
    pn = '000A569011' 
group by pn;

但是根据您的数据库有多大，可能表现不佳，请全部尝试，看看哪个最适合您