Relationship Within The Table.

Primary Key
The key is called the primary key.With the primary key, even if there is a record in other fields of the twin.This record is still a different record.

Foreign Key
Foreign keys are essentially "opposite" of the primary key. Primary key is the parent table and foreign keys are in the child table.

TYPES OF RELATIONSHIP

> One-to-one (1:1)
> One-to-Many (1:M)
> Many-to-One (M:1)
> Many-to-many (M:N)