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...
What is Equivalence of Functional Dependencies in DBMS? In the context of databases,functional dependency is a relationship between two setsof attributes within a database table. It describes the dependency of one set of attributes, known as the dependent attributes, on another set of attributes, ...
Therefore, we must know how to calculate closure set of functional dependencies before Normalization. A functional dependency from "A" to "B" is said to be trivial if "B" is a subset of "A".ExampleIn the corresponding relation,Tuple A C t1 a1 c1 t2 a1 c1 t3 a2 c2 t3 a2 c2 t4 a3...
AfunctionaldependencyXYisnon-trivial(非平凡函数依赖)ifYX= {supervisor_id}{specialization} Non-trivialFDsaregivenimplicitlyintheformofconstraintswhendesigningadatabase. Forinstance,thespecializationofastudentsmustbethesameasthatofthesupervisor. ...
(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 ...
DBMS Functional Dependency MCQs: This section contains multiple-choice questions and answers on functional dependency in DBMS. Submitted byAnushree Goswami, on March 31, 2022 1. Two attributes can be functionally ___ on/of each other. Dependent ...
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 ...