Question

Which clause in the SQL standard controls how NULL values in a composite foreign key are handled when comparing to a primary key.

(a) SET

(b) MATCH

(c) ON DELETE

(d) ON CASCADE

The question was asked during an interview.

This key question is from Foreign Keys and Referential Integrity in portion Using SQL to Manage Data of MySQL

Answer 1

Correct answer is (b) MATCH

The explanation: The MATCH clause in the SQL standard controls how NULL values in a composite (multiple-column) foreign key are handled when comparing to a primary key. MySQL essentially implements the semantics defined by MATCH SIMPLE.