Question

What is a correlated sub-query?

(a) An independent query that uses the correlation name of another independent query.

(b) A sub-query that uses the correlation name of an outer query

(c) A sub-query that substitutes the names of the outer query

(d) A sub-query that does not depend on its outer query’s correlation names

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

This intriguing question originated from Nested Subqueries in portion Introduction to Relational Model and Sql of RDBMS

Answer 1

Right answer is (b) A sub-query that uses the correlation name of an outer query

The best I can explain: A correlated sub-query is the one that uses the correlation name of an outer query.