How to use Concatenation option in Foreign Key

Question

Hi,
I have 2 tables.
Master Table : Father(a varchar2(10),b varchar2(10)
Child Table : Child (c varcahr2(20))
In the child Table i have stored the following Father.A||Father.B
Child.C = Father.a + Father.B
I want to create a Foreign Key Relation for this.
I cant use '||' option.
Can any one please guide me.
ALTER TABLE child ADD CONSTRAINT fk_child FOREIGN KEY (c) REFERENCES father(a||b)
ON DELETE CASCADE;
This statement throws error.
Pls help me in this

Answer 1

Why not create a third column on the Master table ?
alter table Father add c varchar2(20);
-- then perform an update
update Father set c := a|| b
commit
/and then create the constraint as;
ALTER TABLE child ADD CONSTRAINT fk_child FOREIGN KEY (c) REFERENCES father (c) ON DELETE CASCADE;