How to write a query with count - mysql

Question

I have two tables as follows:
==================
StudentsClasses
----------------
ID (Registration ID of the class)
StudentID (ID of student taking class)
ClassID (ID of certain class)
----------------
==================
Students
---------------
ID (ID of student)
Name (Name of student)
GradeLevelID (Grade of student)
---------------
==================
And they are joined by StudentsClasses.StudentID and Students.ID.
I am trying to write a query to return the students with the least classes registered. My query is:
SELECT Students.Name, COUNT(StudentsClasses.StudentID) AS Expr1
FROM StudentsClasses INNER JOIN
Students ON StudentsClasses.StudentID = Students.ID
GROUP BY StudentsClasses.StudentID, Students.Name
ORDER BY Expr1
However, that only returns all the students with at least 1 class in ASC order.
I know the correct answer is 7 students with 0 classes.
How can I modify my query to return only those 7 students with 0 classes.

Answer 1

To enlist those students, that have no classes, instead of INNER JOIN you should be using LEFT JOIN here, to make sure all rows from students table are listed, even though there is no rows in studentclasses for that particular student.
SELECT
s.name, count(sc.id) AS classes
FROM
students s
LEFT JOIN studentsclasses sc ON s.id = sc.studentid
GROUP BY s.name
HAVING count(sc.id) = 0 -- added after comment
ORDER BY count(sc.id);
OR another method (for retrieving only students that have 0 classes):
SELECT
s.name
FROM
students.s
LEFT JOIN studentsclasses sc ON s.id = sc.studentid
WHERE
sc.id IS NULL

Answer 2

This should limit your results to those students having whatever the minimum number of registered classes is (so if the minimum is currently zero, then zero, if it becomes true that the least number of registrations is 3, then it will use 3, etc.)
select s.name,
v.classes
from students s
join (
select s.name,
count(sc.id) as classes
from students s
left join studentsclasses sc
on s.id = sc.studentid
group by s.name
order by count(sc.id)
limit 1
) v
on s.name = v.name

Answer 3

Answers for this question.
How can I modify my query to return only those 7 students with 0 classes.
SELECT
s.name, count(sc.id) AS classes
FROM
students s
LEFT JOIN studentsclasses sc ON s.id = sc.studentid
where (SELECT count(sc.id) FROM
students s
LEFT JOIN studentsclasses sc ON s.id = sc.studentid)=0
GROUP BY s.name
ORDER BY count(sc.id);