Which keys are an attribute or combination of attributes on the many side of a one-to-many relationship in a database?

In a one-to-many relationship within a database, the key that represents the many side of the relationship is a foreign key. The foreign key is a field (or a combination of fields) in one table that uniquely identifies a row of another table or the same table that refers to one unique row.

In this context, the table on the many side will include a foreign key that links back to the primary key in the table on the one side of the relationship. This linking is crucial, as it establishes the relationship between the two tables, allowing you to reference the associated records appropriately.

The primary key, while critical, is used to identify records uniquely on the one side of the relationship. Compound keys involve multiple attributes but do not specifically denote the relational aspect present in a one-to-many setup. Secondary keys may refer to alternate identifiers in a database, but again, they do not inherently establish the relationship reflected by a foreign key. Therefore, foreign keys are specifically designed for this purpose, making them the correct answer in the context of a one-to-many relationship.