Question

出于某种原因，这似乎很容易，但我无法弄清楚。所以我有一个名为“contest_entries”的表，其中有“username”和“rating”列。

表格如下所示：

Username | rating | Contest_id
John     | 3      |   4
Mike     | 1      |   4
Eric     | 3      |   5
Mike     | 1      |   6
John     | 2      |   7
Mike     | 1      |   8 
John     | 1      |   9

因此，对于不同的比赛，人们可以置于不同的位置，

我的问题是如何显示用户名赢得了多少次比赛，获得了第二名或第三名（获得第一名，又名为= 1，第二名被评为= 2，第三名被评为= 3）并列出所有即使用户名从未使用过第1，第2，第3，用户名也是如此。然后最终根据谁获胜最多（谁拥有最多“评级= 1”）对他们进行排名。

所以它看起来像这样：

Username   |  Ranking | 1st places | Second Places | Third Places
Mike       |     1    |    3       |    0          |    0
John       |     2    |    1       |    1          |    1
Eric       |     3    |    0       |    0          |    1

etc etc.

Answer 1

SELECT x.username
     , COUNT(CASE WHEN rating = 1 THEN 'foo' END) first 
     , COUNT(CASE WHEN rating = 2 THEN 'foo' END) second 
     , COUNT(CASE WHEN rating = 3 THEN 'foo' END) third
  FROM ratings x 
 GROUP 
    BY username;

Answer 2

尝试

SELECT username, @n := @n + 1 ranking, `1st places`, `2nd places`, `3rd places`
  FROM
(
  SELECT username,
  SUM(CASE WHEN rating = 1 THEN 1 ELSE 0 END) `1st places`,
  SUM(CASE WHEN rating = 2 THEN 1 ELSE 0 END) `2nd places`,
  SUM(CASE WHEN rating = 3 THEN 1 ELSE 0 END) `3rd places`
    FROM Table1
   GROUP BY username
   ORDER BY `1st places` DESC
) q, (SELECT @n := 0) n

输出：

| USERNAME | RANKING | 1ST PLACES | 2ND PLACES | 3RD PLACES |
-------------------------------------------------------------
|     Mike |       1 |          3 |          0 |          0 |
|     John |       2 |          1 |          1 |          1 |
|     Eric |       3 |          0 |          0 |          1 |

这是 SQLFiddle 演示

MySQL的简单统计页面排名

2 个答案: