REDUCED TO value-expr ,...

    Allows you to eliminate duplicate values for fields in a record
    stream and to group the records in a relation according to
    unique field values. However, only using the REDUCED clause
    does not guarantee the sort order within groups and the results
    are unpredictable. To ensure specific order, use the SORTED BY
    clause.

    The value expression, value-expr, specifies a symbol or string of
    symbols used to calculate a value.