Analysis › Develop the Data Model › Relationships › Examples of Relationships

Examples of Relationships

Types of relationships include one-to-one, one-to-many, and many-to-many.

One-to-one Relationship Example

In this example, we have proposals and contracts.

• Each proposal sometimes results in one contract.
• Each contract sometimes is the result of one proposal.

This is an example of a one-to-one optional relationship.

Note: The line crossing the relationship line indicates one.

One-to-many Relationship Example

In this example, we have employees and dependents.

• Each employee sometimes claims one or more dependents.
• One employee always claims each dependent.

This is an example of the most common relationship, a one-to-many optional-on-the-many-side relationship.

Note: The crow’s foot indicates the “many” and the “o” on the line indicates that the relationship is optional.

Many-to-many Relationship Example

In this example, we have products and warehouses.

• Each product sometimes is stored in one-or-more warehouses.
• Each warehouse sometimes stores one-or-more products.

This is an example of a many-to-many relationship.

What would be the relationship membership cardinality and optionality for Golfer maintains Scoring Record?