Which database constraint establishes a link between two tables by referencing a primary key in another table?

Which database constraint establishes a link between two tables by referencing a primary key in another table?

• A. Primary key
• B. Constraints
• C. Schema
• D. Foreign key

Answer: (D)

Relational databases connect information across tables with keys to maintain referential integrity. A foreign key is a column (or set of columns) in one table that references the primary key in another table. This creates a link between the two tables and ensures that every value in the foreign key exists as a corresponding primary key in the referenced table. The primary key itself identifies rows within its own table, not across tables, so it’s not the mechanism that links tables. Constraints is a broad term for rules, and schema describes the database structure, not the linking relationship. If defined, foreign keys can also govern actions on updates or deletions to preserve consistency.

Relational databases connect information across tables with keys to maintain referential integrity. A foreign key is a column (or set of columns) in one table that references the primary key in another table. This creates a link between the two tables and ensures that every value in the foreign key exists as a corresponding primary key in the referenced table. The primary key itself identifies rows within its own table, not across tables, so it’s not the mechanism that links tables. Constraints is a broad term for rules, and schema describes the database structure, not the linking relationship. If defined, foreign keys can also govern actions on updates or deletions to preserve consistency.