Question

What is the functions of on delete cascade?

(a) It is used to delete a tuple in a table

(b) It is used to specify the precise attribute that needs to be deleted in a single relation.

(c) It is used to preserve referential integrity in a relation

(d) It is used to execute sub-queries in the from clause.

The question was asked by my college professor while I was bunking the class.

Question is from Integrity Constraints in section Intermediate and Advanced Sql of RDBMS

Answer 1

Right choice is (c) It is used to preserve referential integrity in a relation

The explanation is: It is used to preserve referential integrity in the relation. When an attribute of a relation is the foreign key in another relation, deleting it causes referential integrity problems. The on delete cascade solves this problem by forcing us to delete the foreign key first.