Types of Relationships
Before you begin to establish relationships between tables in the database, you must know what types of relationships can exist between a given pair of tables. Knowing how to identify them properly is an invaluable skill for designing a database successfully.
There are three specific types of relationships that can exist between a pair of tables: one-to-one, one-to-many, and many-to-many. The tables participate in only one type of relationship at any given time. (You'll rarely need to change the type of relationship between a pair of tables. Only major changes in either of the table's structures could cause you to change the relationship.)
The discussion for each type of relationship begins with a generic example ...