Re: prevent 2 users update same row?

I'm not sure, where is your goal. For the named statements of course there is no other way to work as you described. You try to change to columns by statement T4 and close the transaction immedeately. wo things has to be done:

1. Set the database server to the correct isolation level.
2. Use SELECT FOR UPTDATE with a following UPDATE CURSOR

and you'll see: it works

Best regards
Gerhard

mergler_at_my-deja.com schrieb:

> The scenario I am trying to prevent is as follows:
>
> T1 User A 'SELECT * from TBL WHERE ID=1'
> T2 User B 'SELECT * from TBL WHERE ID=1'
> T3 User A 'UPDATE TBL SET COL1='FOO',COL2='FOO-TOO' WHERE ID=1' then
> COMMIT
> T4 User B 'UPDATE TBL SET COL1='FOO-FOO',COL2='' WHERE ID=1' then
> COMMIT
>
> T4 has just overwritten the update from T3. Any changes made by T3 are
> gone. Is this a problem? Yes, according to my customer! :(
>
> To me this is quite an obscure occurence of events and I question the
> real need to prevent this (in our application, its not likely to happen
> unless you *try* to do it), but nevertheless we must prevent this.
>
> I have tried using sequences within triggers and using the SELECT FOR
> UPDATE clause and I have found that I cannot prevent T4 from occuring.
> I could be doing something wrong of course, but I would sincerely
> appreciate any insight, past experience, or voodoo and/or magic tricks
> that can prevent this scenario from occuring. Thanks!
>
> Regards,
> Jeff Mergler
> QSI Corporation
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.

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Gerhard Eberlein
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