Re: Re: Re: mySQL with Perl

I'm only really familiar with mySQL. But is that a mySQL specific command? Or is that common among SQL in general? I your reasoning for doing this completely. And now that I've heard your views on the issue, I'd like to implement such a feature into my coding as well. But I'd like to keep my code generalized should I need to change the SQL database in the future (maybe to postgres, or something).

Thanks,

--Coplan

Comment on Re: Re: Re: mySQL with Perl

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Re (4): mySQL with Perl by VSarkiss (Monsignor) on Nov 11, 2002 at 22:08 UTC
The `exists` clause is standard SQL, at least SQL-92, so it should be supported by most if not all platforms. Note that "supported" doesn't equate to "works well". There are several ways to achieve concurrency control, and what I showed is not necessarily the best way (granted that "best" varies from circumstance to circumstance). You could also use user-defined transactions, though I think not every MySQL back-end supports those. Or you could define a unique key on the user name, and catch the error if you try to insert a duplicate. I said "Be careful" to the code you showed mainly because it was leaving a pretty wide window where someone could get a row in between the test and the insert.	[reply] [d/l]

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Re (4): mySQL with Perl
by VSarkiss (Monsignor) on Nov 11, 2002 at 22:08 UTC

The exists clause is standard SQL, at least SQL-92, so it should be supported by most if not all platforms. Note that "supported" doesn't equate to "works well".

There are several ways to achieve concurrency control, and what I showed is not necessarily the best way (granted that "best" varies from circumstance to circumstance). You could also use user-defined transactions, though I think not every MySQL back-end supports those. Or you could define a unique key on the user name, and catch the error if you try to insert a duplicate. I said "Be careful" to the code you showed mainly because it was leaving a pretty wide window where someone could get a row in between the test and the insert.

[reply]
[d/l]