mapping many to many items - sql

Question

I'm using database that looks like this the following:
CREATE TABLE Students(
[StudentId] [int],
...,
[MajorId] [int]
);
CREATE TABLE Majors(
[MajorId] [int],
...,
[MajorDes] [varchar](20)
);
CREATE TABLE CourseRequiredForEachMajor(
[MajorId] [int],
...,
[CourseTitle] [varchar](20)
);
CREATE TABLE CoursesCompletedByStudents(
[StudentId] [int],
...,
[CourseTitle][varchar] (20)
);
INSERT INTO Majors ([MajorId] , .. , [MajorDes]) VALUES (1, ... . 'IT');
INSERT INTO Students ([StudentId], .. , [MajorId]) VALUES (1, ... . 1);
INSERT INTO CourseRequiredForEachMajor ([MajorId], .. , [CourseTitle]) VALUES (1, ... . 'IT101');
INSERT INTO CourseRequiredForEachMajor ([MajorId], .. , [CourseTitle]) VALUES (1,...,'IT302');
INSERT INTO CourseRequiredForEachMajor ([MajorId], .. , [CourseTitle]) VALUES(1,...,'IT321');
INSERT INTO CoursesCompletedByStudents ([StudentId], .. , [CourseTitle]) VALUES (1, ... . 'IT101');
INSERT INTO CoursesCompletedByStudents ([StudentId], .. , [CourseTitle]) VALUES (1,...,'IT302');
INSERT INTO CoursesCompletedByStudents ([StudentId], .. , [CourseTitle]) VALUES(2,...,'IT321');
I'm trying to list the missing courses for each student in order to complete the all the requirements for each major ( e.g. in the image above, I want to say that studentId# 1 need to take course IT321 in order to complete all requirement for majorId #1 ).
Also is there anyway that I can do to show percentage of completion ? ( e.g. studentId#1 completed two courses ( 66.6% ) out of 3 courses that are required by the major ). what is the way to do the calculations of this.
I really have no idea how to solve this, but this is my attempt:
Select CoursesCompletedByStudents.CourseTitle from Students,MajorsCourseRequiredForEachMajor,CoursesCompletedByStudents
where Students.MajorId= Major.MajorId and Studetns.StudentId = CoursesCompletedByStudents.[StudentId]
and CourseRequiredForEachMajor.[CourseTitle]=CoursesCompletedByStudents.[CourseTitle]

Answer 1

This query would give the required result.
with coursesCTE as
(
Select StudentId, CourseTitle, m.MajorId
from Students s
join Majors m
on s.MajorId = m.MajorID
join CourseRequiredForEachMajor cr
on cr.MajorId = m.MajorID
),
completedCTE
as
(
Select StudentId, cc.courseTitle, MajorId
from CoursesCompletedByStudents cc
join CourseRequiredForEachMajor cm
on cc.CourseTitle = cm.CourseTitle
)
Select * from coursesCTE
except
Select * from completedCTE
If you want comma separated course Ids, you can use the Stuff/XML path hack or STRING_AGG if you're using SQL Server 2017