MySQL：数据透视表计数

Question

我需要 SQL 方面的帮助来将此表转换

===================
| 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   |
===================

为：

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

我可以进行简单的计数等，但正在努力尝试使用派生信息来旋转表。任何帮助表示赞赏。

Answer 1

使用：

  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

Answer 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

Answer 3

只是添加@OMG 答案的快捷方式。
您可以消除 CASE 语句：

SELECT t.fk,
         SUM(t.status = 100) AS count_100,
         SUM(t.status = 101) AS count_101,
         SUM(t.status = 102) AS count_102
    FROM TABLE t
GROUP BY t.fk