Delete child records before I can delete the parent

Question

Hello,I'm a newbie to SQL and if it is not to difficult I can succeed to write querie's. I don't much know about PL/SQL.
We are working with Oracle.The parent ERD is this.
Table 1 --> linking Table --> Table 2 --> Table 3(detail)
1 | 1 1 1 1 1 n
|--> Table 1 detail
1
Now I want to delete for every record of table 1 who doesn't have a record in the table 1 detail.
But before I can do this:
- I have to delete the one or more records in table 3,
- then in table 2 and then the records in the linking table
- and at last the records from Table 1, which is the parent.
Can anybody help or put me in a direction how to solve this?
Cascade doesn't work I think.
I mean by 'Linking table' a table with only three UID's(Table 1, Table 3 and his self)
I mean by the numbers the relation between the tables.
I'm working with Toad
Thanks in advance,
Nico

Answer 1

if I am understanding you correctly you have 3 tables kind of like this
create table  table1 as (select 1 t1_id from dual union
                      select 2 from dual union
                      select 3 from dual);
create table      table2 as (select 1 t2_id, 1 t1_id from dual union
                      select 2 t2_id, 1 t1_id from dual union
                      select 3 t2_id, 2 t1_id from dual union
                      select 3 t2_id, 2 t1_id from dual);
create table  table3  as (select 1 t3_id, 1 t2_id from dual union
                      select 2 t3_id, 1 t2_id from dual union
                      select 3 t3_id, 2 t2_id from dual);
select t1_id, t2_id, t3_id
from  table1 left outer join table2 using (t1_id) left outer join table3 using (t2_id)
order by t1_id;
T1_ID     T2_ID     T3_ID
1     1     1
1     1     2
1     2     3
2     3     
3          so you would like to delete table 1 t1_id 2 and 3 because there are no corresponding entris in table 3 (the detail table)
delete from table1 where t1_id in
  select t1_id
from  table1 left outer join table2 using (t1_id) left outer join table3 using (t2_id)
where t3_id is null
select * from table1;
t1_id
1of course that leaves you with orphans so you will need to clean up table 2
delete from table2 where  t1_id not in
(select t1_id from table1);why won't a cascade delete work?
Edited by: pollywog on Nov 18, 2010 12:03 PM