Question

SELECT campus,semester, AVG(CountOfStudents)
FROM
(
  SELECT semester,year,campus, count(*) as CountOfStudents
  FROM regestration
  GROUP BY  semester, year, campus,student_id
) t
GROUP BY   campus,semester

I need to do is to find the average number of people per semester of each campus

My table structure is:

Table name – registration

student_id
campus
year
batch
semester

campus, year, semester and batch these can help identify unique records, where as student_id may repeat itself the query above gives wrong answer.

Answer 1

Follow these steps:

• remove student_ID from the GROUP BY clause and
• add DISTINCT inside COUNT()

query,

SELECT campus, semester, AVG(CountOfStudents)
FROM
(
  SELECT semester, year, campus, count(DISTINCT student_id) as CountOfStudents
  FROM   registration
  GROUP BY  semester, year, campus
) t
GROUP BY   campus, semester