MySQL：枢轴+计数答案

【问题标题】：MySQL: Pivot + CountingMySQL：枢轴+计数
【发布时间】：2010-08-24 23:45:48
【问题描述】：

我需要有关转换此表的 SQL 的帮助：

===================
| Id | FK | Status|
===================
| 1  | A  | 100   |
| 2  | A  | 101   |
| 3  | B  | 100   |
| 4  | B  | 101   |
| 5  | C  | 100   |
| 6  | C  | 101   |
| 7  | A  | 102   |
| 8  | A  | 102   |
| 9  | B  | 102   |
| 10 | B  | 102   |
===================

到这里：

==========================================
| FK | Count 100 | Count 101 | Count 102 |
==========================================
| A  | 1         | 1         | 2         |
| B  | 1         | 1         | 2         |
| C  | 1         | 1         | 0         |
==========================================

我可以如此简单地计数等，但我正在努力尝试使用派生的信息来旋转表格。任何帮助表示赞赏。

【问题讨论】：

标签： sql mysql database pivot aggregate-functions

【解决方案1】：

用途：

  SELECT t.fk,
         SUM(CASE WHEN t.status = 100 THEN 1 ELSE 0 END) AS count_100,
         SUM(CASE WHEN t.status = 101 THEN 1 ELSE 0 END) AS count_101,
         SUM(CASE WHEN t.status = 102 THEN 1 ELSE 0 END) AS count_102
    FROM TABLE t
GROUP BY t.fk

【讨论】：

CASE WHEN t.status = 100 THEN 1 ELSE 0 END = IF(t.status = 100, 1, 0) = t.status = 100

【解决方案2】：

使用：

select * from 
(select fk,fk  as fk1,statusFK from #t
) as t
pivot
(COUNT(fk1) for statusFK IN ([100],[101],[102])
) AS pt

【讨论】：