Best way for for update

Question

Hi all
i'm new for store procedure.I have to make a procedure like this
begin
if(condition)
select for update
update
else
insert
My problem is how to make select for update.If i'm not in fault i think in a procedure i have to make a select into cursor and not a easy select.
Then i don't know how to make this:can i create an empty cursor and fill it when is necessary?
Thanks!!

Answer 1

I'll put it this way-- I accept that it is perfectly possible to build an application that does pessimistic locking correctly. I have never, unfortunately, seen a multiuser application in the wild that actually implemented pessimistic locking correctly. Once you allow a lock to be held while a user does something, you need all sorts of infrastructure to handle cases where users (or their sessions) go splat.
Optimistic locking, on the other hand, is a mere matter of following a pattern (however you choose to implement it). It's far easier to take a team of developers and say
- Thou shalt have a LAST_MODIFIED_DATE on every table you create (optional if you use ORA_ROWSCN)
- Thou shalt select this date each and every time you populate a screen where users will potentially change data
- Thou shalt include the LAST_MODIFIED_DATE in all your updates
- Thou shalt check for 0 row updates and inform the user that the row has changed
You can then enforce these religiously and reliably in code reviews. Pessimistic locking, on the other hand, can't be easily boiled down to commandments that can be beaten into developers (at the point of a lead pipe)-- it requires that everyone understand how transactions work and correctly account for all the failure scenarios. I'd certainly prefer that all developers were able to do that sort of thing, but I wouldn't want to bet the success of my project that they all do.
Justin