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Consider a relation geq which represents “greater than or equal to”, that is, (x, y) ∈ geq only if y ≥ x.
create table geq
(lb integer not null
ub integer not null
primary key lb foreign key (ub) references geq on delete cascade)
Which of the following is possible if a tuple (x, y) is deleted?
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- A tupel (z, w) with z > y is deleted
- A tuple (z, w) with z > x is deleted
- A tuple (z, w) with w < x is deleted
- The deletion of (x, y) is prohibited
- A tupel (z, w) with z > y is deleted
Correct Option: C
When the tuple (x, y) is deleted, consider the tuple (z, w). Now, in tupel (z, w), z is the lower bound and hence > X. and w is the upper bound and hence > Y.
→ (X, Y) will be easily deleted.
Therefore, Y > X
