How to copy existing row value into new row with a trigger. Same table

Question

Oracle guru,
I am looking for a before or after trigger statement that will copy existing values inserted in the previous row into columns A & B. Then insert those values in a new row into column A & B if null? Same table. Hopefully my question is clear enough.
-Oracle 10g express
-I have an existing " before insert trigger" that insert id and timestamps when a new row is created.
-Table is composed of column like id,timestamps,A,B and more.
Thanks in advance
Pierre

Answer 1

957911 wrote:
Oracle guru,
I am looking for a before or after trigger statement that will copy existing values inserted in the previous row into columns A & B. Then insert those values in a new row into column A & B if null? Same table. Hopefully my question is clear enough.
-Oracle 10g express
-I have an existing " before insert trigger" that insert id and timestamps when a new row is created.
-Table is composed of column like id,timestamps,A,B and more.
Thanks in advance
PierreI will call it a very Wrong design.
It is a wrong Table Design. You are duplicating the data in table and not complying with the Database Normalization rules.
How about Verifying if Column A & B are NULL before inserting and inserting another row and avoiding it in Triggers?
If you are bent to achieve this, below code might be helpful. However, I would never go with this approach. If you would care about explaining the reason for going ahead with such a data model, people could suggest better alternative that might conform with Normalization rules.
create or replace trigger trg_test_table
after insert on test_table
for each row
declare
  pragma autonomous_transaction;
begin
  if :new.col_a is null and :new.col_b is null then
    insert into test_table
    select 2, systimestamp, col_a, col_b
      from test_table
     where pk_col = (select max(pk_col) from test_table b where b.pk_col < :new.pk_col);
  end if;
  commit;
end trg_test_table;Read SQL and PL/SQL FAQ and post the mentioned details.
Do not forget to mention output from
select * from v$version;