One-to-One Relationship
- A person has one passport, and each passport belongs to one specific person.
- Every student is assigned a unique student ID, and each ID matches only one student.
- Each person owns one car, and each car is owned by one person.
One-to-Many Relationship
- One customer places many orders, but each order is linked to a single customer.
- A company can have several phone numbers, but every phone number belongs to only one company.
- One car maker builds multiple models, but each model is made by only one car maker.
- One city is in one country, but a country has many cities.
Many-to-Many Relationship
- Students and classes: A student can register for many classes, and a single class can have many students enrolled.
- Customers and products: Each customer can buy several products, and every product can be purchased by various customers.
- Users and roles: A user can have multiple roles, and each role can be assigned to multiple users in a system.
Just in case I blank out.