Creating relationships in the relational model: Which construct is used to relate rows across two tables (parent and child)?

Introduction / Context:
Relational databases link tables through referential constraints, enabling normalized designs while preserving navigability across entities.

Given Data / Assumptions:

• A parent table has a primary (or candidate) key.
• A child table references that key to relate its rows.
• Standard SQL referential integrity rules apply.

Concept / Approach:
A foreign key in the child table references the candidate/primary key in the parent table. This enforces referential integrity: each foreign key value must match an existing parent key or be null (subject to constraints).

Step-by-Step Solution:

Verification / Alternative check:
SQL DDL (FOREIGN KEY ... REFERENCES ...) codifies this mechanism.

Why Other Options Are Wrong:
Composite keys: Can be foreign or candidate keys but don’t by themselves create relationships.
Determinants / candidate keys: Important internally; relationships are implemented via foreign keys.

Common Pitfalls:
Confusing a parent’s primary key (identifier) with the child’s foreign key (reference); both are needed to form the link.

Final Answer:
foreign keys.