在同一列上计数查询

Question

以下是两个SQL表：

• 课堂（1-100），
• 性别（男/女）

我想计算每个教室的每个性别。我希望查询结果为：

Classroom | CountMale | CountFemale
          |           |
          |           |
          |           |

如何计算？

Answer 1

SELECT Classroom,
SUM(CASE WHEN Gender='male' THEN 1 ELSE 0 END) as CountMale,
SUM(CASE WHEN Gender='female' THEN 1 ELSE 0 END) as CountFemale
FROM t
GROUP BY Classroom

Answer 2

也许是这样的：

SELECT Classroom, 
      SUM(CASE WHEN GENDER = 'MALE' THEN 1 ELSE 0 END) AS CountMale,
      SUM(CASE WHEN GENDER = 'FEMALE' THEN 1 ELSE 0 END) AS CountFemale
FROM TABLE
GROUP BY Classroom

更改文字。