Multi-Table Foreign Key

Question

Hi all
I am using oracle 9i, is it possible to create foreign key that referenced by more than one table, for example if I have such field I want the value for this field be referenced by values exist in either Table X or Table Y.
Message was edited by:
giggs11

Answer 1

Hi,
If I understood your question, and if you want that a value in one table should exist in both tables X and Y, then this is possible.
SQL> create table x (id number constraint pk_x primary key);
Table created.
SQL> create table z (id number constraint pk_z primary key);
Table created.
SQL> create table a (id number);
Table created.
SQL> alter table a add constraint fk_a_x foreign key (id) references x;
Table altered.
SQL> alter table a add constraint fk_a_z foreign key (id) references z;
Table altered.
SQL> insert into x values (1);
1 row created.
SQL> insert into z values (1);
1 row created.
SQL> insert into a values (1);
1 row created.
SQL> delete from x;
delete from x
ERROR at line 1:
ORA-02292: integrity constraint (A.FK_A_X) violated - child record found
SQL> delete from z;
delete from z
ERROR at line 1:
ORA-02292: integrity constraint (A.FK_A_Z) violated - child record found
SQL> insert into x values (2);
1 row created.
SQL> insert into a values (2);
insert into a values (2)
ERROR at line 1:
ORA-02291: integrity constraint (A.FK_A_Z) violated - parent key not found
SQL> insert into z values (2);
1 row created.
SQL> insert into a values (2);
1 row created.Cheers
Legatti