Question

Consider the relation R(A, B) in which (AB) is the primary key and the relations S(A, C) where A is the primary key. Assume there are no null values and no foreign keys or integrity constraints.
$Q_1\text{: Select A from R where A in (Select A from S)}$
$Q_2\text{: Select A from S where A in (Select A from R)}$

Which of the following option is correct related to the above queries?

• A. $Both{Q}_{1}and{Q}_2\text{gives same result.}$
• B. None of these
• C. $Both{Q}_{1}and{Q}_2\text{may gives same result.}$
• D. $Both{Q}_{1}and{Q}_2\text{gives different result.}$

Answer 1

The correct option is C $Both{Q}_{1}and{Q}_2\text{may gives same result.}$

For the same values unique for the column A in tables R and S.
$Q_{1}and{Q}_2\text{will give the same output.}$