Delete entries over 1 month old in parent and child tables

Question

Hi guys,
Im new to oracle (2days old) and im struggling to find out how to delete all entries over 1 month old in a database but also delete entries from the child table. I have read about delete cascading etc but im really strugging at the moment. Any tip or ideas? thank you

Answer 1

You just need to delete data in parent table using the right WHERE clause that requires some timestamp column that stores data age. If the foreign key constraint is created with ON DELETE CASCADE child rows are automatically deleted.
Assuming P is the parent table and C the child table and the timestamp column is stored in the parent table here is an example.
SQL> create table p(px int primary key, d date);
Table created.
SQL> create table  c(cx int, cy int references p on delete cascade);
Table created.
SQL>
SQL> insert into p values(1, '01/01/2011');
1 row created.
SQL> insert into p values(2, '15/01/2011');
1 row created.
SQL> insert into p values(3, '31/01/2011');
1 row created.
SQL> insert into c values(10,1);
1 row created.
SQL> insert into c values(20,2);
1 row created.
SQL> insert into c values(30,3);
1 row created.
SQL> commit;
Commit complete.
SQL>
SQL> delete p where months_between(sysdate, d) >= 1;
2 rows deleted.
SQL>
SQL> select * from p;
        PX D
         3 31-01-2011
SQL> select * from c;
        CX         CY
        30          3
SQL>Edited by: P. Forstmann on 15 févr. 2011 13:45