Re: FK and NULL values

Peter Aku wrote:
> FK1 is a foreign key defined on table B. FK1 is composed
> of more than one column.
>
> If NULLs are allowed on those columns (FK1) in table B,
> when a row which contains NULLs on any of the columns that
> compose FK1, ORACLE allows these NULLs to be inserted,
> as expected. However, no validation is performed on the
> foreign key constraint. Inconsistent values may be
> introduced through this kind of addition or update
> exercise.
>

  Oracle practices match none. As a result, if one of the columns in the composite foreign key is null, it can insert into the child table. As a result, you can restricts not null column constraint on each column of the foreign key or add a check table constraint to check your null situation.

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Name   : Lun Wing San
Title  : Oracle Application Developer of Hong Kong Productivity Council
         Oracle Database Administrator and System Administrator of QRC
Phone  : (852)27885841