Relational database design

Relational database design are the best system analysis.

One should be able to specify how entities within a given entity set and relationships within a given relationship set are distinguished.There are some subset of attributes of a relational schema R present with the property that no two tuples in any relation instance r of R should have the same combination of values for these attributes.

Closure of a Set of functional Dependencies

We say that such functional Dependencies are logically implied by F.

          Suppose we are given a relation schema R=(A,B,C,G,H,I) and the set of functional Dependencies

                       A ➡️ B

                       A ➡️ C

                     CG ➡️ H

                     CG ➡️ I

                        B ➡️ H

The functional Dependency

                        A ➡️ H

is logically implied i.e.we can show that whenever our given set of functional Dependencies holds,A ➡️ H must also hold.Suppose that t1 and t2 are tuples such that

                 t1[A] = t2[A]

Since we are given that A ➡️ B, it follows from the definition of functional Dependency that

                t1[B] = t2[B]

Then, since we are given that B ➡️ H, it follows from the definition of functional Dependency that

                t1[H] = t2[H]

Therefore,we have shown that, whenever t1 and t2 are tuples such that t1[A] = t2[A],must be that t1[H]. But that is exactly the definition of A ➡️ H.

                                

                                   Atul Raja Kujur

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