Any field that is part of a key is never stored as null. (A null key does not have a well-defined position in relation to other keys.) If a key field has an illegal value, the field is stored in the database as described here:
| Illegal LOW-VALUES | minimum possible value (0 or -99999...)
minimum possible date value (01/01/01) |
| Illegal HIGH-VALUES | maximum possible value (99999...)
maximum possible date value (database dependent) |
| Illegal SPACES | zero (or 01/01/01 for a date field) |