SELECT s.name FROM Student s, Program p where s.subjectid=p.subjectid
An inner join may be implicitly specified by the use of a cartesian product in the FROM clause and a join condition in the WHERE clause. In the absence of a join condition, this reduces to the cartesian product.
The main use case for this generalized style of join is when a join condition does not involve a foreign key relationship that is mapped to an entity relationship.
select c from Customer c, Employee e where c.hatsize = e.shoesize
In general, use of this style of inner join (also referred to as theta-join) is less typical than explicitly defined joins over entity relationships.
this given query does not qualify for cartesian join because there is relationship defined between them although join not being used here.