SQL correct way of joining if the other parameter is null

Question

I have this code and its temporary tables so you can run it.

create table #student
(
    id int identity(1,1),
    firstname varchar(50),
    lastname varchar(50         


        

Answer 1

This should get you started:

-- filter out the student and quiz you want
DECLARE @qid INT = 1
DECLARE @sid INT = 1

SELECT * 
FROM #student AS s
INNER JOIN #quiz AS q  -- you want the quiz
 ON 1=1
LEFT OUTER JOIN #quiz_details AS qd  -- left join here to get result where rows not found
 ON qd.id = q.id 
 AND qd.student_id=s.id
WHERE s.id = @sid
 AND q.id = @qid
 AND qd.id IS NULL -- only return quizes not taken