The REDUCED TO clause lets you eliminate duplicate values for
    fields in a record stream. You can use this expression to
    eliminate redundancy in the results of a query and to group
    records in a relation according to unique field values.

1  –  Examples

    The following programs demonstrate the use of the REDUCED TO
    clause and the SORTED clause with a single relation. These
    programs sort the records in the EMPLOYEES relation on the basis
    of STATE. The REDUCED TO clause limits the record stream so that
    each record in the stream has a different value for the field
    STATE. The programs then display the list of states represented
    in the EMPLOYEES relation.

1.1  –  C Example

    #include <stdio.h>
    DATABASE PERS = FILENAME "PERSONNEL";

    main ()
    {
    READY PERS;
    START_TRANSACTION READ_ONLY;

    FOR E IN EMPLOYEES
       REDUCED TO E.STATE
       SORTED BY E.STATE
          printf("%s\n", E.STATE);
    END_FOR;

    COMMIT;
    FINISH;
    }

1.2  –  Pascal Example

    program reduced_one_rel (input,output);
    DATABASE PERS = FILENAME 'PERSONNEL';

    begin
    READY PERS;
    START_TRANSACTION READ_ONLY;

    FOR E IN EMPLOYEES
       REDUCED TO E.STATE
       SORTED BY E.STATE
          writeln (E.STATE);
    END_FOR;

    COMMIT;
    FINISH;
    end.

2  –  Format

  (B)0reduce-clause =

    qqqqq> REDUCED TO qqqwqqqqqq> db-field qqqwqqq>
                         mqqqqqq<qqqq , <qqqqqj

2.1  –  Format arguments

    db-field               A database field value expression. A
                           database field value expression is a field
                           name qualified with a context variable.
                           The database field must be defined in
                           the current context of the statement.
                           For example, the database field must be
                           defined in the context of the START_STREAM
                           or DECLARE_STREAM statements or the FOR
                           loop. See the DB_Field help entry for more
                           information.