How to aggregate results in many to many Query - mysql

Question

I have 3 tables in my database:
Student:
id
name
Student_Course:
student_id
course_id
Course:
id
grade
And I want to list all the students and the results of whether they have pass all of the course they have chosen . Assuming that grade <= 'C' is pass.
I tried sql like:
SELECT s.*,
IF('C'>=ALL(SELECT c.grade FROM from Course c WHERE c.id=sc.course_id),1,0) as isPass
FROM Student s LEFT JOIN Student_Course sc on sc.student_id=s.id
This sql works, but if now I want a column 'isGood' which means all the grade='A', do I need to execute the subquery again? How can I get both 'isGood' and 'isPass' by executing subquery only once?

Answer 1

I believe the grade would be better served in the junction table. Using that, I have created a scenario that might help you solve your question:
Scenario
create table student (id int, fullname varchar(50));
insert into student values (1, 'john'), (2, 'mary'), (3, 'matt'), (4, 'donald');
create table course (id int, coursename varchar(50));
insert into course values (1, 'math'), (2, 'science'), (3, 'business');
create table student_course (student_id int, course_id int, grade char(1));
insert into student_course values
(1, 1, 'C'), (1, 2, 'C'), (1, 3, 'C'),
(2, 1, 'A'), (2, 2, 'A'), (2, 3, 'A'),
(3, 1, 'A'), (3, 2, 'C'), (3, 3, 'C'),
(4, 1, 'A'), (4, 2, 'C'), (4, 3, 'F');
Query
select s.*, case when all_a_grades.student_id is not null then 'GOOD' else 'MEH' end as grades
from student s
left join (
-- find students who got A in all classes
select student_id, count(distinct ca.id) as aclasses, count(distinct sc.course_id) as allclasses
from student_course sc
left join (select id, 'A' as agrade from course) ca
on ca.id = sc.course_id and ca.agrade = sc.grade
group by student_id
having aclasses = allclasses
) all_a_grades on all_a_grades.student_id = s.id
where not exists (
-- let's make sure we filter OUT students who have failed
-- at least one course
select 1
from (
-- find students who have failed at least one course
select distinct student_id
from student_course
where grade not in ('A', 'B', 'C')
) t where t.student_id = s.id
)
Result
| id | fullname | grades |
| 1 | john | MEH |
| 2 | mary | GOOD |
| 3 | matt | MEH |