A record selection expression (RSE) defines specific conditions
    individual records must meet before Oracle Rdb includes them in a
    record stream. RSE clauses let you:

    o  Include all records in the relation

    o  Eliminate duplicate records

    o  Limit the number of records returned

    o  Test for values and conditions

    o  Sort the records in the record stream

    o  Combine records from the same or different relations

    The RDML rse clauses are:

    o  CROSS

    o  FIRST

    o  REDUCED

    o  SORTED

    o  WITH

    For more information and the syntax diagrams see the HELP entry
    for each of these clauses.