GATE CSE 2002 | Relational Algebra Question 30 | Database Management System

GATE CSE 2002

MCQ (Single Correct Answer)

-0.3

With regard to the expressive power of the formal relational query languages, which of the following statements is true?

Relational algebra is more powerful than relational calculus.

Relational algebra has the same power as relational calculus.

Relational algebra has the same power as safe relational calculus.

None of the above

GATE CSE 2000

MCQ (Single Correct Answer)

-0.3

Given the relations

employee (name, salary, deptno), and
department (deptno, deptname, address)

Which of the following queries cannot be expressed using the basic relational algebra operations $$\left(\sigma, \pi,\times ,\Join, \cup, \cap,-\right)$$?

Department address of every employee

Employees whose name is the same as their department name

The sum of all employee’s salaries

All employees of a given department

GATE CSE 1999

MCQ (Single Correct Answer)

-0.3

Consider the join of a relation R with a relation S. If R has m tuples and S has n tuples then the maximum and minimum sizes of the join respectively are

m + n and 0

mn and 0

m + n and |m – n|

mn and m + n

GATE CSE 1999

MCQ (Single Correct Answer)

-0.3

The relational algebra expression equivalent to the following tuple calculus expression:

$$\left\{ {t|t \in r \wedge \left( {t\left[ A \right] = 10 \wedge t\left[ B \right] = 20} \right)} \right\}$$ is:

$${\sigma _{\left( {A = 10 \vee B = 20} \right)}}\left( r \right)$$

$${\sigma _{\left( {A = 10} \right)}}\left( r \right) \cup {\sigma _{\left( {B = 20} \right)}}\left( r \right)$$

$${\sigma _{\left( {A = 10} \right)}}\left( r \right) \cap {\sigma _{\left( {B = 20} \right)}}\left( r \right)$$