next up previous
Next: Dependency Preservation Up: Desirable Properties of Decomposition Previous: Desirable Properties of Decomposition

Lossless-Join Decomposition

  1. We claim the above decomposition is lossless. How can we decide whether a decomposition is lossless?

    Why is this true? Simply put, it ensures that the attributes involved in the natural join ( tex2html_wrap_inline1634 ) are a candidate key for at least one of the two relations.

    This ensures that we can never get the situation where spurious tuples are generated, as for any value on the join attributes there will be a unique tuple in one of the relations.

  2. We'll now show our decomposition is lossless-join by showing a set of steps that generate the decomposition:

Osmar Zaiane
Thu Jun 18 12:56:34 PDT 1998