Composite Foreign Keys

You learn something new every day...  Today I found a table that nobody could figure out - turns out it's sole purpose in life is to maintain foreign key relationships (via data) so the objects knew how to verify referential integrity before inserting.  After a little googling I found out that it is possible to have a composite foreign key.  Crazy I thought...  but it works.  If anyone has any (negative) experience in this area I would love to hear about it.

(Note I am now living with one foot in SQL Server land and the other in Oracle Land - hence the semicolons)

create table tmp1 (   f1  char(1),   f2  char(1),   primary key (     f1, f2) );   create table tmp2 (   f1  char(1),   f2  char(1)   , constraint FK_composite foreign key (f1, f2) references tmp1 (f1, f2) ); insert into tmp1 (f1, f2) values ('1', '1'); insert into tmp1 (f1, f2) values ('2', '2'); -- succeeds insert into tmp2 (f1, f2) values ('1', '1'); insert into tmp2 (f1, f2) values ('2', '2'); -- fails insert into tmp2 (f1, f2) values ('1', '2'); insert into tmp2 (f1, f2) values ('2', '1'); select * from tmp1; select * from tmp2; drop table tmp2; drop table tmp1;