Database 1. Let A4, A5, and A6 be attributes in a relation R. If both of these functional dependencies hold: A4 → A5 and A5 → A6, then A4 → A6holds, because of the rule.
2. The fact that the value of a foreign key attribute must exist in another set of one or more key attributes in another table, is called a(n) .
3. Any set of attributes that allows us to identify unique rows (tuples) in a given relation are known as super keys. Out of these super keys we can always choose a proper subset among these which can be used as a key. Such keys are known as keys. If there is a combination of two or more attributes which is being used as the primary key then we call it as a key.