Question

我桌子的简化版本：

 -------------------------------------------
| sender | recipient | date       | amount  |
 -------------------------------------------
| A      | B         | 2016-01-01 | 500.00  |
| C      | B         | 2016-01-02 | 600.00  |
| D      | C         | 2016-01-03 | 1025.00 |
| D      | D         | 2016-01-04 | 300.00  |
| D      | D         | 2016-01-05 | 300.00  |
| D      | D         | 2016-01-06 | 300.00  |
| D      | D         | 2016-01-07 | 300.00  |
| D      | D         | 2016-01-08 | 300.00  |
 -------------------------------------------

如何获得recipient行OR LESS行至少amount 1024.00或更多？

不会D，因为它不会有3行超过amount 1024.00。

预期结果：

 -----------
| recipient |
 -----------
| B         |
| C         |
 -----------

Answer 1

查询非常简单：

select recipient
from table
group by recipient
having count(*) <= 3 and sum(amount) >= 1024

Answer 2

这很棘手。关键的观察是三个最高值的总和将超过1024，如果有的话，那么。

在MySQL中，您可以使用变量执行此操作：

select recipient, sum(amount) as amount_3
from (select t.*,
             (@rn := if(@r = recipient, @rn + 1,
                        if(@r := recipient, 1, 1)
                       )
             ) as rn
      from t cross join
           (select @r := '', @rn := 0) params
      order by recipient, amount desc
     ) t
where rn <= 3
group by recipient
having sum(amount) >= 1024;

Answer 3

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我将如何解决此查询？

3 个答案: