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Database-Management-System
August 29, 2024
Database-Management-System
August 29, 2024
Database-Management-System
August 29, 2024
Database-Management-System
August 29, 2024

Database-Management-System

Question 509
There exists a construct which returns a value ‘true’ if the argument subquery is :
A
empty
B
non-empty
C
in error
D
none of the above
Question 509 Explanation: 
The exists construct returns the value true if the argument subquery is nonempty.
1. exists r ⇔ r ≠ ∅
2. not exists r ⇔ r = ∅
Correct Answer: B
Question 509 Explanation: 
The exists construct returns the value true if the argument subquery is nonempty.
1. exists r ⇔ r ≠ ∅
2. not exists r ⇔ r = ∅

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