field <str> is not unique in previous relations in the CROSS

  Explanation:  You specified a field that does not exist  in  the
  previous relations specified by the CROSS clause.

  User  Action:   The  relation  definition  associated  with  the
  context variable does not include a definition for the specified
  field.  You may have specified the wrong context  variable  with
  the field or mistyped the field name.