Table Relationships
Relational databases are powerful because of the relationships between the tables. These relationships help us to keep our databases clean and efficient. A relationship between tables assumes that one of these tables has a foreign key that references the primary key of another table.
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Types of Relationships
There are 3 primary types of relationships in a relational database:
- One-to-one
- One-to-many
- Many-to-many
One-to-one
A one-to-one relationship most often manifests as a field or set of fields on a row in a table. For example, a user will have exactly one password.
Settings fields might be another example of a one-to-one relationship. A user will have exactly one email_preference and exactly one birthday.