The dependency of an attribute on a set of attributes is known as trivial functional dependency if the set of attributes includes that attribute. Symbolically: A ->B is trivial functional dependency if B is a subset of A. The following dependencies are also trivial: A->A & B->B For exa...
A functional dependency from "A" to "B" is said to be trivial if "B" is a subset of "A". Example In the corresponding relation, Tuple A Ct1 a1 c1 t2 a1 c1 t3 a2 c2 t3 a2 c2 t4 a3 c3 t5 a3 c2A → C holds ast1[A] = t2[A] then t1[C] = t2[C] t3[A] = t3[A]...
What are Armstrong's Axioms in Functional Dependency in DBMS?Armstrong axioms are a complete set of inference rules or axioms, introduced and developed by William W. Armstrong in 1974. The inference rules are sound which is used to test logical inferences of functional dependencies. The axiom ...
AfunctionaldependencyfromXtoYexistsifandonlyif: Foreveryinstanceof|R|ofR,iftwotuplesin|R|agreeonthevaluesoftheattributesinX,thentheyagreeonthevaluesoftheattributesinY WewriteXYandsaythatXdeterminesY ExampleonStudent(sid,name,supervisor_id,specialization): ...
(An example of an inclusion dependency is the sentence that says that every MANAGER is an EMPLOYEE.) If, however, the sentences of interest are inclusion dependencies and unrestricted functional dependencies, then there need not exist an Armstrong database. This result holds even if we allow ...
Starting from SQL-99, the concept of “functional dependency” was introduced; a column B is functionally dependent on columns {A1, A2} in a result set if all rows which share the same value of A1 and the same value of A2 necessarily share the same value of B. Then ...
6. Which of the following is a type of functional dependency? Trivial Functional Dependency Non-trivial Functional Dependency Both A and B None of the above Answer:C) Both A and B Explanation: There are mainly four types of Functional Dependency in DBMS: ...