The following table has two attributes X and Y where X is the primary key and Y is the foreign key referencing X with on-delete cascade.
|
X |
Y |
|
2 |
4 |
|
3 |
4 |
|
4 |
3 |
|
5 |
2 |
|
7 |
2 |
|
9 |
5 |
|
6 |
4 |
The set of all tuples that must be additionally deleted to preserve referential integrity when the tuple (3, 4) is deleted is:
1
(4, 3), (2, 4) and (6, 4)
2
(4, 3), (2,4), (6, 4), (5, 2) and (7, 2)
3
(3, 4), 4, 3), (2,4), (6, 4), (5, 2), (7, 2) and (9, 5)
4
(4, 3), (2,4), (6, 4), (5, 2), (7, 2) and (9, 5)