Getting Around Key Constraint

Question

Table A is a parent of Table B, where Table B really only serves as an intermediary table associating Table A's records with some Table C (also a parent of table B).
As such, Table B is FK'd as a child of both Tables A & C. In order to delete records from Table A, a subquery against table B must be performed (relating table A and table C's fields).
So my task is to purge certain records from this schema based on the composite key in table C.
This is the order I have to go in because of the key constraints:
Delete From table B
Delete From table A
Delete From table C
However, in order to delete from table A, its children rows in record B must be accessed because the entire deletion stems off a subquery select with a composite key from table C (which must then be translated through table B to get to the correct records in table A)
Naturally, the DBAs didn't enable cascade delete anywhere in this entire schema (sigh). I have no ability to change anything about the database, and because of a number of concerns, I can't write to a temp table and I can't pull anything at all into the executing program's memory.
Is there anyway to do this. (Sorry if Table A/B/C is confusing. I can give them real names later)

Answer 1

Hi,
Have a look at this sample:
This code
drop table transaction cascade constraints;
drop table Invoice cascade constraints;
drop table Invoice_Transaction cascade constraints;
create table Transaction
  ID_ NUMBER,
  LBL_T VARCHAR2(50 CHAR)
create table Invoice
  ID_ NUMBER,
  LVL_I VARCHAR2(50)
create table Invoice_Transaction
  ID_TRANSACTION NUMBER,
  ID_INVOICE NUMBER
alter table transaction add constraint t_pk primary key(id_);
alter table invoice add constraint i_pk primary key(id_);
alter table Invoice_Transaction add constraint it_pk primary key(id_transaction,id_invoice);
alter table Invoice_Transaction add constraint it_t foreign key (id_transaction) references transaction(id_);
alter table Invoice_Transaction add constraint it_i foreign key (id_invoice) references invoice(id_);
insert into transaction values (1,'NA1');
insert into transaction values (2,'NA2');
insert into invoice values (1,'I1');
insert into invoice values (2,'I2');
insert into invoice values (3,'I3');
insert into invoice values (4,'I4');
insert into invoice_transaction values (1,1);
insert into invoice_transaction values (1,2);
insert into invoice_transaction values (1,3);
insert into invoice_transaction values (2,4);
commit;
select lbl_t, lvl_i
from transaction t, invoice i, invoice_transaction it
where t.id_ = it.id_transaction
and i.id_ = it.id_invoice;
create or replace procedure remove_transaction(pIdTrans IN NUMBER)
IS
  CURSOR cInvTrans IS
      SELECT id_invoice
      FROM Invoice_Transaction
      WHERE id_transaction = pIdTrans
      FOR UPDATE;
BEGIN
  FOR vInvTrans IN cInvTrans
  LOOP
    DELETE FROM Invoice_Transaction WHERE CURRENT OF cInvTrans;
    DELETE FROM invoice WHERE id_ = vInvTrans.id_invoice;
  END LOOP;
  DELETE FROM TRANSACTION WHERE ID_ = pIdTrans;
  COMMIT;
END;
CALL remove_transaction(1);
select lbl_t, lvl_i
from transaction t, invoice i, invoice_transaction it
where t.id_ = it.id_transaction
and i.id_ = it.id_invoice;
Generates this output
drop table transaction succeeded.
drop table Invoice succeeded.
drop table Invoice_Transaction succeeded.
create table succeeded.
create table succeeded.
create table succeeded.
alter table transaction succeeded.
alter table invoice succeeded.
alter table Invoice_Transaction succeeded.
alter table Invoice_Transaction succeeded.
alter table Invoice_Transaction succeeded.
1 rows inserted
1 rows inserted
1 rows inserted
1 rows inserted
1 rows inserted
1 rows inserted
1 rows inserted
1 rows inserted
1 rows inserted
1 rows inserted
commit succeeded.
LBL_T                                              LVL_I                                             
NA1                                                I1                                                
NA1                                                I2                                                
NA1                                                I3                                                
NA2                                                I4                                                
4 rows selected
procedure remove_transaction(pIdTrans Compiled.
CALL remove_transaction(1) succeeded.
LBL_T                                              LVL_I                                             
NA2                                                I4                                                
1 rows selectedHTH!
Yoann.