Doesn't this basic FK constaint lead to catch22 scenario?

Question

Version:11g
What would you do if you wanted to UPDATE a column in the parent table like the one below?
Its a bit of CATCH-22 situation. I can't update the parent table without updating the child table and i can't update the child table without updating the parent table.
create table parent
(identity number,
ename  varchar2(45)
alter table parent
  add constraint parent_PK primary key (IDENTITY);
insert into parent values (600,'John');
insert intp parent values (700,'Steve');
create table child
(child_id number,
domainid number,
emp_city varchar2(45)
alter table child
add constraint child_FK1 foreign key (domainid)
references parent (IDENTITY);
insert into child values (1,600,'Amsterdam');
SQL> select * from parent;
  IDENTITY ENAME
       600 John
SQL> select * from child;
  CHILD_ID   DOMAINID EMP_CITY
         1        600 Amsterdam
SQL> update parent set identity=700 where identity=600;
update parent set identity=700 where identity=600
ERROR at line 1:
ORA-02292: integrity constraint (SCOTT.CHILD_FK1) violated - child record found
SQL> update child set domainid=700 where domainid=600;
update child set domainid=700 where domainid=600
ERROR at line 1:
ORA-02291: integrity constraint (SCOTT.CHILD_FK1) violated - parent key not found

Answer 1

You can use a deferred constraint
Constraint is checked at commit instead of at the end of the DML...
SQL> alter table child
  2  add constraint child_FK1 foreign key (domainid)
  3  references parent (IDENTITY)
  4  INITIALLY DEFERRED;
Tabella modificata.
SQL> insert into child values (1,600,'Amsterdam');
Creata 1 riga.
SQL> select * from parent;
  IDENTITY ENAME
       600 John
SQL> select * from child;
  CHILD_ID   DOMAINID EMP_CITY
         1        600 Amsterdam
SQL> update parent set identity=700 where identity=600;
Aggiornata 1 riga.
SQL> select * from child;
  CHILD_ID   DOMAINID EMP_CITY
         1        600 Amsterdam
SQL> commit;
commit
ERRORE alla riga 1:
ORA-02091: transaction rolled back
ORA-02292: integrity constraint (BUONI.CHILD_FK1) violated - child record found
SQL> update parent set identity=700 where identity=600;
Aggiornata 1 riga.
SQL> update child set DOMAINID =700 where DOMAINID =600;
Aggiornata 1 riga.
SQL> commit;
Commit completato.Max
[My Italian Oracle blog|http://oracleitalia.wordpress.com/2010/01/17/supporto-di-xml-schema-in-oracle-xmldb/]
Edited by: Massimo Ruocchio on Jan 18, 2010 10:06 AM