Question

Consider a schema R(A, B, C, D) and functional dependencies A -> B and C -> D. Then the decomposition of R into R1 (A, B) and R2(C, D) is

(a) dependency preserving and lossless join

(b) lossless join but not dependency preserving

(c) dependency preserving but not lossless join

(d) not dependency preserving and not lossless join

The question was asked in semester exam.

My query is from Materialized Views topic in portion Query Processing Techniques of Database Management

Answer 1

Right answer is (d) not dependency preserving and not lossless join

To explain: While decomposing a relational table we must verify the following properties:

i) Dependency Preserving Property

ii) Lossless-Join Property.