One to many relationship is a type of cardinality that refers to a relationship between two entities in an entity relational diagram (between two tables in a database). A simple example would be a binding between the entities order and item. Each order may have multiple items, but a product (e.g., a TV) may be delivered within a single order.
Graphically, a one-to-many relationship is usually represented in a logical model with crow’s foot notation on one side of the relationship.
One-to-many relationships in Luna Modeler
Each time you create a new relationship between tables, a one to many relationship is created.
How to create a new one to many relationship
- Add two tables to the ER diagram: order and item.
- Then create a new relationship. On the toolbar, click the Relationship button and first click the order table and then the item table.
Alternate solution – JSON
However, there are more options that may be suitable for similar cases. JSON data types can also be used.
Types of relationships in ER diagrams
- One-to-one relationships
- One-to-many relationships
- Many-to-many relationships