Question

这是我的数据集和当前代码：http://sqlfiddle.com/#!2/f9a605/3

| id | courseid | username |  day  | score |
--------------------------------------------
| 1  |    2     |   tim    | may 5 |  85   |
| 2  |    2     |   mike   | may 6 |  86   |
| 3  |    2     |   tim    | may 7 |  82   |
| 4  |    3     |   tim    | may 8 |  80   |
| 5  |    2     |   mike   | may 9 |  79   |
| 6  |    2     |   joe    | may 10|  81   |

我想为每个用户的最低分数选择值，其中courseid = 2按最低分数排序，因此结果应如下所示：

| mike | may 9  | 79 | 
| joe  | may 10 | 81 | 
| tim  | may 8  | 82 |

我目前的代码如下：

SELECT  courseid, username, day, MIN(score) FROM    result where courseid = '2' GROUP BY username order by MIN(score) limit 10

我目前的结果如下：

| mike | may 6  | 79 |
| joe  | may 10 | 81 |
| tim  | may 5  | 82 |

日子不对。

当courseid = 2时，如何获得与该人的最低分数相对应的正确日期？

Answer 1

这可以使用2个条件的自联接来完成，一个是用户名，另一个是最低分

SELECT  r.courseid, r.username, r.`day`,r.score
FROM    result r
JOIN (SELECT username, MIN(score) score 
      FROM result 
      where courseid = '2'
      GROUP BY username) r1
ON(r.username = r1.username and r.score = r1.score)
order by r.score
limit 10

同样在您的预期结果中，蒂姆应该具有may7的日期

`Fiddle Demo`

Answer 2

您可以使用子查询：

select courseid, username, day, score
  from result x
 where score = (select min(y.score)
                  from result y
                 where y.username = x.username
                   and x.courseid = y.courseid)
   and courseid = 2
 order by score

<强>小提琴：

http://sqlfiddle.com/#!2/f9a605/36/0

mysql选择column2的值，其中MIN（column1）

2 个答案:

`Fiddle Demo`