Re: Uniquely identifying a record in SQL without a unique key?

[Michael Ryan <michaelrtr@xxxxxxxxx>]

If you're using a cursor, you can use UPDATE WHERE CURRENT OF...


On Fri, Dec 28, 2012 at 1:54 PM, James H. H. Lampert <
jamesl@xxxxxxxxxxxxxxxxx> wrote:

> I'm beginning to study Scott Klement's JDBCR4 API, as a means of
> extending our QuestView product to access external databases (and it
> would also allow us to expand our very limited support of data types
> that are normally SQL-only), and something suddenly struck me:
>
> Suppose I'm looking at a record, and I decide to make a change to it.
> And the file isn't uniquely keyed.
>
> Now, with native RLA, we can easily determine the RRN of the record
> we're looking at, and acquire an update lock on that record by its RRN.
> After all, RRNs only change if a RGZPFM is done, and that requires an
> exclusive lock on the member.
>
> But now, suppose I have to use SQL, JDBC, and the JDBCR4 API. I'm no
> expert on SQL (SQL for Dummies is still my primary reference on the
> subject), but I don't recall ever reading anything anywhere about a way
> to get a record's RRN, or retrieve a record by its RRN, from SQL.
>
> I must be missing *something* here, but what? How do I guarantee that an
> update will go to the right record, when I initially read it without a
> lock, and apparently can't grab a lock on it by its RRN?
>
> --
> JHHL
> --
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