SQL查询列的百分比

Question

如何查询下表中的学生出勤率百分比

Name    Attendance
A   1
B   0
B   1
B   1
B   1
B   1
B   1
A   0
A   0
A   0

Answer 1

我建议Sum(Attendance) / Count(Attendance)为百分比：

  select Name,
         Sum(Attendance) / Count(Attendance) * 100 as Percentage
    from MyTable
group by Name

因此，对于A学生，我们有Sum(Attendance) == 1 + 0 + 0 + 0 = 1和Count(Attemdance) == 4，且百分比为1 / 4 * 100 = 25