Re: Changing isolation level?

While stranded on information super highway D Alpern wrote:
:)SELECT... FOR UPDATE {WAIT | NOWAIT} springs to mind...
:)

No, you cannot select for update when you just want to read the data, it will lock out everyone else.

:) David
:)
:)(rm ns beside @ in return email address)
:)
:)On Thu, 4 Dec 2003 05:59:46 +1100, "Howard J. Rogers"
:)<hjr_at_dizwell.com> wrote:
:)
:)>
:)>Time to don the Devil's Advocate costume, I think.
:)>
:)>I can think of lots of cases where it would be rather unfortuate to see an
:)>old piece of data just prior to it being changed. Rather than see the old
:)>data, I could well imagine that it would be more helpful to see nothing
:)>until the situation stabilises.
:)>
:)>If I have a customer demanding to know whether I have a turbo-widget in
:)>stock, I can select from my products table to check. It tells me I have one
:)>such item left. Mrs. Miggens therefore, on the strength of that, undertakes
:)>the arduous two-hour journey from remote rural New South Wales into the City
:)>Centre to pick up said turbo-widget. Unbeknownst to her, however, the
:)>information I gave her was wrong, because at the time I did my query, Fred
:)>in the next cubicle was selling the same product to Miss Marple. He hadn't
:)>committed the transaction, which is why I saw a stock level of 1. But it
:)>would have been nice not to give the wrong info out to Mrs. Miggens. I
:)>suppose I could have badgered her into placing an order, because then my
:)>attempt to update the stock level myself would have failed. But Mrs. Miggens
:)>ran into a bit of credit rating trouble a while back, and doesn't have a
:)>credit card. The most she can do on the phone is to enquire.
:)>
:)>There are two choices there, I suppose: see nothing at all (the blocking
:)>idea). Or see a stock level of 0 (the dirty reads issue beloved of, er,
:)>certain other products). Oracle's long-time answer has been: you'll see 1,
:)>and only 1, and nothing else, ever... which some might consider to be a lack
:)>of choice in answering technology.
:)>
:)>Regards
:)>HJR
:)>
:)>
:)>
:)>
:)

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