Which statement differentiates identifying relationships from non-identifying relationships?

• A. In identifying relationships, the child primary key includes the parent key.
• B. In non-identifying relationships, the child primary key includes the parent key.
• C. Identifying relationships involve no key changes.
• D. Non-identifying relationships require the child to include the parent key.

Answer: (A)

The distinguishing feature is how the child table’s primary key is formed in the relationship. In identifying relationships, the child’s primary key includes the parent’s key, so the parent’s identifier becomes part of the child’s identifier. This reflects a strong link where the child cannot be uniquely identified without the parent. In non-identifying relationships, the child keeps its own primary key, and the parent’s key is stored as a separate foreign key rather than being incorporated into the child’s primary key.

For example, an OrderLine might be identified by a combination of OrderID (the parent key) and LineNumber. That demonstrates the identifying type. In contrast, a Customer and Order example would have Order with its own OrderID as primary key, and the Order would store CustomerID as a foreign key without changing its own primary key—illustrating a non-identifying relationship.

So the correct statement highlights that the child primary key includes the parent key in identifying relationships.