HP 3000 Manuals

ALLBASE/SQL Performance Guidelines

Using Fetch Unique Scans 

Fetch Unique is a special faster kind of index scan method which is
automatically used when a predicate meets the following criteria:

   *   There is exactly one EQUAL factor for each key column.
   *   All factors must be exactly matching with a unique index.
   *   No non-unique index columns occur in the WHERE clause.
   *   The factors in the WHERE clause are ANDed together.
   *   There are no indicator variables in the WHERE clause.
   *   Data retrieval is done with a singleton SELECT, not a cursor.  (A
       singleton operation is one in which only a single row qualifies.)

Providing a non-cursor SQL SELECT, UPDATE, or DELETE meets these
criteria, it uses a Fetch Unique scan.

MPE/iX 5.0 Documentation