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Next: Selection Operation Up: Query Processing Previous: Query Interpretation

Equivalence of Expressions

  1. The first step in selecting a query-processing strategy is to find a relational algebra expression that is equivalent to the given query and is efficient to execute.
  2. We'll use the following relations as examples:

     Customer-scheme = (cname, street, ccity)

    Deposit-scheme = (bname, account#, name, balance)

    Branch-scheme = (bname, assets, bcity)

    We will use instances customer, deposit and branch of these schemes.

Osmar Zaiane
Sun Jul 26 17:45:14 PDT 1998