1
GATE CSE 2024 Set 2
+2
-0.66

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

A

1

B

2

C

3

D

4

2
GATE CSE 2021 Set 1
Numerical
+2
-0.67

A relation r(A, B) in a relational database has 1200 tuples. The attribute A has integer values ranging from 6 to 20, and the attribute B has integer values ranging from 1 to 20. Assume that the attributes A and B are independently distributed. The estimated number of tuples in the output of σ(A>10)∨(B=18)(r) is ______

3
GATE CSE 2019
Numerical
+2
-0.67
Consider the following relations P(X,Y,Z), Q(X,Y,T) and R(Y,V).

How many tuples will be returned by the following relational algebra query?
4
GATE CSE 2018
+2
-0.6
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 $$Q$$?

A
$${\sigma _{B < 5}}\left( {r\,\,} \right.$$ $$\bowtie$$ $$\left. {\,\,s} \right)$$
B
$${\sigma _{B < 5}}\left( {r\,\,LOJ\,\,s} \right)$$
C
$$r\,\,LOJ\,\,\left( {{\sigma _{B < 5}}\left( s \right)} \right)$$
D
$${\sigma _{B < 5}}\left( r \right)LOJ\,\,s$$
GATE CSE Subjects
EXAM MAP
Medical
NEET