Question

Which of the following statements about the FOREIGN KEY constraint is INCORRECT?​

A) Ensures referential integrity
B) Links two tables
C) Can be applied to multiple columns
D) Cannot span multiple tables

Answer 1

The INCORRECT statement about the FOREIGN KEY constraint is that it cannot span multiple tables. In fact, FOREIGN KEY constraints must span multiple tables to link them and maintain referential integrity.

Step-by-step explanation:

The INCORRECT statement about the FOREIGN KEY constraint is D) Cannot span multiple tables.

FOREIGN KEY constraints are used to ensure referential integrity within a relational database by linking columns in one table to columns of another table. They can indeed span multiple tables by linking a column or a set of columns from one table to the primary key columns of another table, which is typically in a different table. It is true that a FOREIGN KEY constraint can be applied to multiple columns, known as a composite foreign key, but it remains within the context of a relationship between two tables.

To summarize, a FOREIGN KEY constraint does ensure referential integrity (A), can link two tables together (B), and can be applied to multiple columns (C). However, statement D is incorrect as FOREIGN KEY constraints are inherently meant to span across tables to establish a relationship between them.