How to get both present and absent students for a year

Question

I need to get the total no. present and absent students in a year from a table attendance: Here is my query:

SELECT if( status = 'P',count(level_id), 0) AS present, 
       if(status='A',count(student_id), 0) AS Absent 
        FROM attendance WHERE level_id = 'L1' AND date LIKE '2016%'

But this returns the total no. of students to either present or absent section.

Answer 1

The problem is that you misunderstood what COUNT(...) does in the query. If you really want to count based on being absent or present, then you can use SUM(...) with a conditional step inside.

SELECT
    SUM(if(status = 'P', 1, 0)) AS Present
    SUM(if(status = 'A', 1, 0)) AS Absent
FROM
    attendance
WHERE
    level_id = 'L1' AND date LIKE '2016%'

Answer 2

Return 1 if you need to count th element:

 SELECT SUM(if( status = 'P',1, 0)) AS present, SUM(if(status='A',1, 0)) AS Absent
 FROM attendance WHERE level_id = 'L1' AND date LIKE '2016%'

Answer 3

Try group by clause like:

SELECT 
 status, 
 count(student_id) as attendance 
FROM attendance 
WHERE level_id = 'L1' 
  AND date LIKE '2016%' 
GROUP BY status;

It will give you the count for each status available in table

Answer 4

这将起作用：

SELECT DISTINCT(student_name), SUM(status = 'P') AS present, SUM(status='A') AS Absent FROM attendance GROUP BY student_name where date LIKE '2016%'