Designing the Data Structure › Using the Data Structure List › One-to-Many Relationships

One-to-Many Relationships

A one-to-many relationship is illustrated in the following Illustration.

1:M Relationship

This illustration is a data model fragment showing:

• Each CUSTOMER entity sometimes places (relationship membership) one or more ORDER entities.
• Each ORDER entity is placed by (relationship membership) exactly one CUSTOMER.

The identifier of CUSTOMER is an attribute called CUSTOMER NUMBER.

The following illustration is a Data Structure List showing the implementation of the figure “1:M Relationship” as a foreign key.

Implementation of the 1:M Relationship

The ORDER table includes a Foreign Key (FK) column called FK_CUSTOMERNUMBER. For any ORDER, the number of the CUSTOMER that places it is stored in that column. This will allow your application user to access from the ORDER table the CUSTOMER who placed an ORDER or the ORDERS a CUSTOMER has placed.