Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
|
Question 509
|
There exists a construct which returns a value ‘true’ if the argument subquery is :
|
empty
|
|
|
non-empty
|
|
|
in error
|
|
|
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 = ∅
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 = ∅
1. exists r ⇔ r ≠ ∅
2. not exists r ⇔ r = ∅