How to select a specific record from MySQL database
You can use sum() and select case, std_id above 3 will be 0
select * from ( select sum(case when std_id in (1, 2, 3) then 1 else 0 end) tot , course_id from std_course group by course_id) t1 where t1.tot <= 3
You can try this using join:
select * from std_course left outer join course on course.id= std_course.course_id where std_id <=3
The query that work for me after the changings in query Answered by @ϻᴇᴛᴀʟ is:
select * from ( select sum(case when std_id in (1,2,3) then 1 else -1 end) tot , course_id from std_course group by course_id) t1 where t1.tot = 3