Display total count of students [closed]

Display total count of students enrolled in all subjects and helping material is

student (rollNumber, Sfname, Slname, email,phone)
Subjects(Subid, subTitle, credit_hrs)
std_sub(rollNUmber (fk from student), subid(fk frim subjects), session, sectionID)

and I wrote query

select subTitle,Subid,rollNumber,rollNUmber 
from student s 
join std_sub st on s.rollNumber=st.rollNUmber 
join subjects sub on sub.subid=st.subid 

But it still needs modification

Answer

If I get you correctly then you want to find out total_students per subject.

Count() which will display number of students enrolled in each subject and any subject has no students then it will show 0 as student count

select 
    subTitle,
    Subid,
    coalesce(count(st.rollNumber), 0) as total_students

from subjects sub 

left join std_sub st 
on sub.subid = st.subid 

left join student s
on st.rollNumber = s.rollNUmber

group by 
    subTitle,
    Subid

Students with no enrollment

select
    rollNumber,
    Sfname,
    Slname
from student
where rollNumber not in (
    select
        distinct rollNumber
    from std_sub
)