SQL Query percentage of a column

Question

how to query percentage of students attendance in table below

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

can i plz have the reason of down vote to prevent in future question the mistake — Mellad Qarizada, Feb 07 '17 at 06:59
http://stackoverflow.com/questions/3061655/getting-percentage-of-count-to-the-number-of-all-items-in-group-by . I think your question has been already resolve in this — DevD, Feb 07 '17 at 07:00
I think it is not easy to know what the table means. There is no date information. How should I interpret this? How are the rows updated? Isn't the table with many columns for different days and with fixed number of names better for your purpose? — ghchoi, Feb 07 '17 at 07:04
select sum(Attendance = 0) / sum(Attendance = 1) * 100 from students — Mellad Qarizada, Feb 07 '17 at 07:10

score 0 · Accepted Answer · answered Feb 07 '17 at 07:07

I suggest Sum(Attendance) / Count(Attendance) as a percentage:

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

So, in case of A student we have Sum(Attendance) == 1 + 0 + 0 + 0 = 1 and Count(Attemdance) == 4 and the percentage is 1 / 4 * 100 = 25

1 Answers1