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 ATTACH, DECLARE ALIAS, or CREATE DATABASE, 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.