Best practice for update/insert on existing/non existing rows

Question

Hello,
In an application I want to check if a row exists and if yes I want to update the row and if not I want to insert the row.
Currently I have something like this:
begin
select *
into v_ps_abcana
from ps_abcana
where typ = p_typ
and bsw_nr = p_bsw_nr
and datum = v_akt_date
for update;
exception
when no_data_found then
v_update := false;
when others then
raise e_error_return;
end;
if v_update = false
then
/* insert new row */
else
/* update locked row */
end if;
The problem is that the FOR UPDATE lock has no effect for inserts. So if another session executes this part exactly the same time then there will be two rows inserted.
What is the best way to avoid this?

Answer 1

for me the 1st solution is the most efficient one.
in your 2nd solution it seems to me that you're gonna create a dummy table that will serve as a traffic cop. well that possible but not the proper and clean approach for your requirement. you're absolutely complicating your life where in fact Oracle can do it all for you.
First thing that you have to consider is your database design. This should somehow corresponds to the business rule and don't just let the program to do it on that level leaving the database vulnerable to data integrity issue such as direct data access. In your particular example, there's no way you can assure that there'll be no duplicate records in the table.
this is just an advice when designing solution: Don't use a "Mickey Mouse" approach on your design!