How to do mathematical comparision with SQL CASE statement - sql

Question

I have a student table around 100k records and I have two types of data in it: student name and level type with selection values primary, secondary, intermediate & university
I want to filter out the student from this table, whose have count > 0, in all level primary, secondary, intermediate & university
I was able to find the sum for each student in each level using the following query
SELECT
student_id,
SUM(CASE WHEN lev_type = 'primary' THEN 1 ELSE 0 END) AS primary,
SUM(CASE WHEN lev_type = 'secondary' THEN 1 ELSE 0 END) AS secondary,
SUM(CASE WHEN lev_type = 'intermediate' THEN 1 ELSE 0 END) AS intermediate,
SUM(CASE WHEN level_type = 'university' THEN 1 ELSE 0 END) AS university
FROM
student_details
GROUP BY
student_id
and I am getting a result like (note that my result is 92242 row(s))
attendee_id primary secondary intermediate uni
student1 0 1 1 2
student2 0 1 1 0
student3 88 209 92 32
student4 0 1 1 0
student5 0 1 1 0
How to filter out student3 from this result?

Answer 1

You can simply add a where statement as follows:
SELECT student_id,
SUM(case when lev_type = 'primary' then 1 else 0 end) as primary,
SUM(case when lev_type = 'secondary' then 1 else 0 end) as secondary ,
SUM(case when lev_type = 'intermediate' then 1 else 0 end) as intermediate ,
SUM(case when lev_type = 'university' then 1 else 0 end) as university
FROM student_details
GROUP BY student_id
WHERE primary = 0 OR secondary = 0 OR intermediate = 0 OR university = 0

Answer 2

HAVING might get you what you want. For example:
SELECT student_id,
sum(case when lev_type = 'primary' then 1 else 0 end) as primary,
sum(case when lev_type = 'secondary' then 1 else 0 end) as secondary ,
sum(case when lev_type = 'intermediate' then 1 else 0 end) as intermediate ,
sum(case when level_type = 'university' then 1 else 0 end) as university
from student_details
group by student_id
-- Put the criteria here by which you want to filter
having sum(case when lev_type = 'primary' then 1 else 0 end) = 0
and sum(case when lev_type = 'secondary' then 1 else 0 end) = 0
and sum(case when lev_type = 'intermediate' then 1 else 0 end) = 0
and sum(case when level_type = 'university' then 1 else 0 end) = 0