sql
create table Courese(
    student varchar(10) primary key,
    class varchar(15)
);

insert into Courese values ('A','math'),('B','en'),('C','math'),('D','bio'),('E','math'),('F','com'),('G','math'),('H','math'),('I','math');

select  * from Courese;

select class from Courese group by class having count(student) >=5 ;

select class from 
(select class,count(student) as num
from Courese group by class)
as tem where num >=5;