On what basis relationship between tables are defined

PROBLEM

---

The question is, if two tables in database are from different entities then how we define relationship between them. i mean can we use some foreign key or any thing to define relationship between them. or we have to create a third table

SOLUTION

---

There is a design principle that states that a table either defines an entity or a relationship but not both. Therefore, use a third table to model the relationship between your two entities -- yes, even if it is 1-1 or 1-N -- noting that the relationship itself may have its own attributes.