Here is a simple relational model. For example, each exam subject has several papers (left two boxes above). Here is some jargon you may come across: The papers are called 'children' of their subject. .They are in a 'one-to-many' relationship. The subject id in the papers table is called a 'foreign key'.
This takes you to the maths subject.
In this way you cen navigate around the whole database structure.
If you go to a subject that has papers, you won't be able to delete it. This is to retain the integrity of the data. You have to delete the papers first. This is called 'referential; integrity'.