There are several answers to this question. Here is what I know!

Relationships help us with reporting and ensure we don’t put data where it shouldn’t be. They are requirement for reporting on two or more tables for  typical reports. Why do they all not have them?

Relationships often make it hard for the programmer to program the front end. Sure they offer security, but when you programmatically input data, they also ensure correctness. So if you are missing them, don’t freak out, your design is not bad or structured incorrectly.

You will just need to learn how to work around it!

Find the common field(s) for the table.

Join those through a query or join them using a tool like Crystal Reports.

Class Recommendation: Relational Database Design