Question

If we specify multiple relations in the from clause and do not specify any conditions in the where clause, what will the result be?

(a) The natural join of both the relations

(b) The left outer join of both the relations

(c) A syntactical error

(d) The Cartesian product of both the relations

The question was posed to me in examination.

Question is taken from Basic Operations in chapter Introduction to Relational Model and Sql of RDBMS

Answer 1

Right choice is (d) The Cartesian product of both the relations

For explanation I would say: If we specify multiple relations in the from clause and do not specify any conditions in the where clause, the default definition given by the from clause is the Cartesian product of the relations listed in the clause. So it returns all the possible combinations of the tuples of the two relations.