Which of the following ensures referential integrity between tables?

A.
Foreign key

B.
CHECK constraint

C.
Index

D.
Primary key

Explanation:
The foreign key ensures referential integrity between tables. A foreign key is a column or combinationof
columns used to establish and enforce a relationship between the data in two tables. This relationshipis
created by adding a column(s) in one of the tables to refer to the other table’s column(s) protected by a
PRIMARY KEY or UNIQUE constraint. This column becomes a foreign key in the first table. A foreign key can
be created by defining a FOREIGN KEY constraint when creating or altering a table.