GATE CSE 2024 Set 2 | Relational Algebra Question 1 | Database Management System

GATE CSE 2024 Set 2

MCQ (Single Correct Answer)

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The relation schema, Person($\underline{\text{pid}}$, $city$), describes the city of residence for every person uniquely identified by $pid$. The following relational algebra operators are available: selection, projection, cross product, and rename.

To find the list of cities where at least 3 persons reside, using the above operators, the minimum number of cross product operations that must be used is

GATE CSE 2019

Numerical

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Consider the following relations P(X,Y,Z), Q(X,Y,T) and R(Y,V).
GATE CSE 2019 Database Management System - Relational Algebra Question 5 English 1

How many tuples will be returned by the following relational algebra query?
GATE CSE 2019 Database Management System - Relational Algebra Question 5 English 2

GATE CSE 2019 Database Management System - Relational Algebra Question 5 English 2

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GATE CSE 2018

MCQ (Single Correct Answer)

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Consider the relations $$r(A, B)$$ and $$s(B, C),$$ where $$s.B$$ is a primary key and $$r.B$$ is a foreign key referencing $$s.B.$$ Consider the query

$$Q:$$ $$\,\,\,\,\,\,\,\,\,$$ $$r$$ $$\,\,\,\,$$ $$\bowtie$$ $$\,\,\,\,$$ $$\left( {{\sigma _{b < 5}}\left( s \right)} \right)$$

Let $$LOJ$$ denote the natural left outer-join operation. Assume that $$r$$ and $$s$$ contain no null values.

Which one of the following queries is NOT equivalent to $$Q$$?

$${\sigma _{B < 5}}\left( {r\,\,} \right.$$ $$\bowtie$$ $$\left. {\,\,s} \right)$$

$${\sigma _{B < 5}}\left( {r\,\,LOJ\,\,s} \right)$$

$$r\,\,LOJ\,\,\left( {{\sigma _{B < 5}}\left( s \right)} \right)$$

$${\sigma _{B < 5}}\left( r \right)LOJ\,\,s$$

GATE CSE 2015 Set 2

MCQ (Single Correct Answer)

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Consider two relations $${R_1}\left( {A,B} \right)$$ with the tuples $$(1,5), (3,7)$$ and $${R_2}\left( {A,C} \right) = \left( {1,7} \right),\left( {4,9} \right).$$
Assume that $$R(A,B,C)$$ is the full natural outer join of $${R_1}$$ and $${R_2}$$. Consider the following tuples of the form $$(A,B,C): a = (1,5,null),$$ $$b = (1,null,7),$$ $$c = (3, null, 9),$$ $$d = (4,7,null),$$ $$e = (1,5,7),$$ $$f = (3,7,null),$$ $$g = (4,null,9).$$ Which one of the following statements is correct?

$$R$$ contains $$a, b, e, f, g$$ but not $$c, d.$$

$$R$$ contains all of $$a, b, c, d, e, f, g.$$

$$R$$ contains $$e, f, g$$ but not $$a, b.$$

$$R$$ contains $$e$$ but not $$f, g.$$