In a one-to-many relationship, where is the foreign key located?

In a one-to-many relationship, the foreign key is placed on the many side of the relationship. This is because the foreign key is used to establish a link between the records in two tables: the primary table (containing the unique values for the primary key) and the secondary table that holds multiple records related to that primary record.

By having the foreign key located on the many side, it allows each record in the secondary table to associate with a single record from the primary table. For instance, if you have a table of customers (the primary table) and a table of orders (the many side), each order in the orders table can link back to one specific customer, thus maintaining the one-to-many relationship.

Other options do not accurately reflect the structure of a one-to-many relationship. The foreign key cannot be on the primary table because the primary table already contains the primary key, not the foreign key. A join table generally facilitates many-to-many relationships and is not applicable here. Lastly, the definition of a primary key itself does not involve foreign keys. Understanding this positioning of the foreign key is crucial for database design and ensuring data integrity.