Database keys are internal pointers to specific table rows in a
 database.  Application programs can use the DBKEY keyword in SQL
 statements to refer to the database key for a table row.

 SQL statements that retrieve rows by specifying their database keys
 have the following advantages:

  o  Fast access:  retrieval through database keys is direct and
     bypasses any indexed or sequential searches.

  o  Reduced locking of data:  since access is direct, the database
     system locks only the row retrieved or updated.

  o  Assurance of uniqueness:  within the database key scope specified
     in CREATE or DECLARE SCHEMA, database keys are guaranteed to be
     unique.  This means singleton SELECT statements based on database
     keys will never return more than a single row, and that they will
     return the exact same row, or an error if it was deleted.