如何组合列，将它们分组然后获得总数？

Question

下面是一个表格，其中包含候选人 ID、他们以面试官姓名参加的两次面试以及每次面试的结果。

candidate_id	interview_1	interview_2	result_1	result_2
1	Interviewer_A	Interviewer_B	Pass	Pass
2	Interviewer_C	Interviewer_D	Pass	Reject

我需要帮助将interview_1和interview_2列合并为一列，并计算每个面试官给候选人的通过和拒绝数，我期望看到的结果如下：

interviewer_name	pass_count	reject_count
Interviewer_A	1	0
Interviewer_B	1	0
Interviewer_C	1	0
Interviewer_D	0	1

SQL 或 Python 都适合我！非常感谢！

Answer 1

在 SQL Server 中，CROSS APPLY 就成了小事

示例

Select [candidate_id]
      ,B.[Interview_name]
      ,pass_count   = case when result='Pass' then 1 else 0 end
      ,reject_count = case when result='Pass' then 0 else 1 end
 From YourTable A
 Cross Apply ( values ([interview_1],[result_1])
                     ,([interview_2],[result_2])
             ) B(Interview_name,result)

结果

candidate_id    Interview_name  pass_count  reject_count
1               Interviewer_A   1           0
1               Interviewer_B   1           0
2               Interviewer_C   1           0
2               Interviewer_D   0           1

Answer 2

您可以将数据集拉两次并合并在一起，我假设它不是一个笨拙的集合。

类似的东西-

WITH combined_set AS(
SELECT
 candidate_id,
 interviewer_1 as interviewer,
 result_1 as result
from candidate_table

UNION

SELECT
 candidate_id,
 interviewer_2 as interviewer,
 result_2 as result
from candidate_table)

SELECT
 interviewer,
 count(case when result = 'Pass' then 1 end) as pass_count,
 count(case when result = 'Reject' then 1 end) as reject_count
FROM combined_set