同一列上有多個計數並插入到另一個表中

Question

我有一個學生表，其中有三列

1. Student Name
2. Class Name
3. Test result

一個學生參加不止一個測試，結果不盡相同。 我正在嘗試將數據放入另一個具有

1. Stundent Name+CLass Name ( Concatenated )
2. Pass (No of tests Passed)
3. Fail (No of tests failed)
4. Absent (No of tests Absent)

我用

select count(*)
from Student 
where Result in ('Passed')
group by StuName, ClassName;

獲取每個stu + class組合通過的科目的計數。 對於失敗和不存在的測試也是如此。

我應該如何修改代碼以插入表二中？

Answer 1

MySQL支持內聯 IF語句，

SELECT  CONCAT(StudentName, ' ', ClassName) Student_Class,
        SUM(test = 'PASSED') totalPass,
        SUM(test = 'Failed') totalFailed,
        SUM(test = 'Absent') totalAbsent
FROM    student
GROUP   BY CONCAT(StudentName, ' ', ClassName)

當您想從上面的查詢中插入結果時，請使用INSERT INTO..SELECT語句，

INSERT  INTO tableNAME(col1, totalPass, totalFailed, totalAbsent)
SELECT  CONCAT(StudentName, ' ', ClassName) Student_Class,
        SUM(test = 'PASSED') totalPass,
        SUM(test = 'Failed') totalFailed,
        SUM(test = 'Absent') totalAbsent
FROM    student
GROUP   BY CONCAT(StudentName, ' ', ClassName)

Answer 2

您可以使用帶有CASE的聚合函數輕松地旋轉數據：

select concat(StuName, ',', ClassName) StuNameClass,
  sum(case when result = 'Passed' then 1 else 0 end) Passed,
  sum(case when result = 'Fail' then 1 else 0 end) Fail,
  sum(case when result = 'Absent' then 1 else 0 end) Absent
from Student 
group by concat(StuName, ',', ClassName);

然后，如果要將數據插入到另一個表中：

insert into Table2 (StudentClassName, Passed, Fail, Absent)
select concat(StuName, ',', ClassName) StuNameClass,
  sum(case when result = 'Passed' then 1 else 0 end) Passed,
  sum(case when result = 'Fail' then 1 else 0 end) Fail,
  sum(case when result = 'Absent' then 1 else 0 end) Absent
from Student 
group by concat(StuName, ',', ClassName);

Answer 3

INSERT INTO t (name_class, passed_count, failed_count, absent_count)
SELECT CONCAT(StuName, ' ', ClassName) AS name_class, 
       SUM(IF(Result='Passed', 1, 0)) AS passed_count, 
       SUM(IF(Result='Failed', 1, 0)) AS failed_count, 
       SUM(IF(Result='Absent', 1, 0)) AS absent_count
FROM Student
GROUP BY StuName, ClassName;