Question

The value in the foreign key column(s).

the foreign key of the referencing relation can be either:
(1) a value of an existing primary key that corresponds to one in the referenced relation
(2) a null
a. Foreign key constraint
b. Referential integrity
c. Primary key
d. Unique key

Answer 1

A foreign key column relates to enforcing referential integrity by containing values that either correspond to a primary key in another table or are null if the relationship is optional.

Step-by-step explanation:

The term foreign key column refers to a field (or collection of fields) in one table that uniquely identifies a row of another table. The purpose of the foreign key is to enforce referential integrity within the database. There are two possible states for a value in a foreign key column: (1) It can be an existing value of a primary key in the referenced table, which ensures that the relationship between the two tables is valid. (2) It can be null if the relationship is optional, meaning that the record in the table with the foreign key does not necessarily need to correspond to a record in the referenced table.