An attribute or a combination of attributes in one table whose values must either match the primary key in another table or be NULL is called ____.
A
Secondary key
B
Super key
C
Candidate key
D
Foreign key
Correct Option:
D
Explanation
A foreign key is an attribute, or set of attributes, whose value normally corresponds to a primary/unique key in another table, or may be NULL when permitted. This relationship helps enforce referential integrity between tables.
