Re: Composite foreign key - null values
Hamzova Katarina wrote:
>
> We had a strange problem. Obviously our tables are designed with
> composite
> primary keys, foreign keys in referencing tables are sometimes null
> allowed.
> Unfortunately we updated several rows with bad (incomplete) FK , we were
> surprised
> that we could do it without error - RI violation.
> So we made some tests
> example
> table A
> column1 PK
> column2 PK
> column3 PK
>
> table B
> column1 null allowed FK --> references table A
> column2 null allowed FK
> column3 null allowed FK
It sounds like you have defined three separate FOREIGN keys but if the
PRIMARY KEY to table A is a composite (three columns) how can you
declare tableB.column 1 as a FOREIGN KEY independent of the other two
columns? Please post a more complete schema, perhaps a dbschema -ss
for each of the two tables so that we can understand.
Art S. Kagel