Question

What is the difference between a join and an outer join operation?

(a) There is no difference

(b) Join preserves a few tuples that are otherwise lost in the outer join

(c) Outer join preserves a few tuples that are otherwise lost in the join

(d) An outer join can be used only on outer queries whereas a join operation can be used in Subqueries

This question was addressed to me during a job interview.

The origin of the question is Join Expressions in chapter Intermediate and Advanced Sql of RDBMS

Answer 1

Correct option is (c) Outer join preserves a few tuples that are otherwise lost in the join

For explanation I would say: The outer join operation preserves a few tuples that are otherwise lost in the join operation. The outer join operation preserves the tuples to the right of the operation.