Suppose that you decompose a schema R (A, B, C, D, E) into two schemas as...

Question

Question

Suppose that you decompose a schema R (A, B, C, D, E) into two schemas as below:

R₁ (A, B, C)

R₂ (C, D, E)

Show that this decomposition is not a lossless join decomposition.

Hint: Take a suitable Relation, r, for the Schema R and show that r is a lossy join decomposition.

engineering Computer-Science

Answer 1

Answer #1

A decomposition {R1, R2} is a lossless-join decomposition

if R1 ∩ R2 → R1 or R1 ∩ R2 → R2 where THis after intersection result must be a candidate key

so

R1 ∩ R2 = Φ

and Φ canot be a candidate key so it is not a lossless join decomposition.

Answer 2

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