The only way around is to write your own FK validation using triggers. I don't think it worth the hassle.

>Thank you very much. I suppose there is not way to get around this rule (otherwise you would mention it) so I will have to make changes.
>
>>You can have NULLs in a FK column but not empty values.
>>
>>>
>>>I am still getting a "conflict" message when trying to create a foreign key constraint. I checked that the table with the foreign key has only those entries in the key column that are present in the unique column of the parent table. The only thing is that the foreign key table has some records with empty value in the foreign key field. Could this be the problem? (I thought that empty column records are not counted in the constraint but maybe I am mistaken).
>>>
>>>TIA.