UGC NET CS 2019 4 December | Question 71

Question 71

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Given two tables R₁(x, y) and R₂(y, z) with 50 and 30 number of tuples respectively, Find maximum number of tuples in the output of natural join between tables R₁ and R₂ ie. R₁ * R₂ ? (* - Natural Join)

1. 1. 30
2. 2. 20
3. 3. 50
4. 4. 1500

Explanation

Natural Join: In this, the two join attributes must have the common attribute in both the relations.

Example: In worst case if all the values of the common attribute are same, then total tuples would be = |m|×|n| = 30×50 = 1500.

R₁

X	Y
Standard 1	CS
Standard 2	CS
Standard 3	CS
⋮	⋮
Standard 50	CS

R₂

Z	Y
Anil	CS
Atul	CS
Jaya	CS
⋮	⋮
30	CS

R₁⨝R₂ : result table after natural join of two tables

X	Y	Z
Standard 1	CS	Anil
Standard 1	CS	Atul
Standard 1	CS	Jaya
⋮	⋮	⋮
Standard 2	CS	Anil
Standard 2	CS	Atul
Standard 2	CS	Jaya
⋮	⋮	⋮
Standard 3	CS	Anil
Standard 3	CS	Atul
Standard 3	CS	Jaya
⋮	⋮	⋮
Standard 50	CS	30
1550	CS	30

So, ∴ Maximum number of tuples in the output of Natural join between relation R1 and R2 = 1500 tuples.

So, option 4 is correct answer

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