Q. If a1, a2, a3 are attributes in a relation and S is another relation, which of the following isan incorrect specification of an integrity constraint? (Solved)
1. primary key(a1, a2, a3)
2. primary key(a1)
3. foreign key(a1, a2) references S
4. foreign key(a1, a2)
- d. foreign key(a1, a2)