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.
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.
