Re: How do you genrate primary keys?

i think thats how mysql does it.

joe

Thomas Day wrote:

>The only other method that I've seen that hasn't been mentioned is to
>generate the primary key of a new row as max(primary_key)+1. Inefficient
>as all get out but I've seen it done on small tables with very low
>volatility where the business rules required absolute sequentiality. It
>worked but I'd only recommend it under very specific circumstances.
>
>
>
>
> Jonathan Gennick
> <jonathan To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> @gennick.com> cc:
> Sent by: Subject: How do you genrate primary keys?
> ml-errors
>
>
> 11/05/2003 08:19
> AM
> Please respond
> to ORACLE-L
>
>
>
>
>
>
>The recent article that mentioned sequences got me to
>thinking. I might pitch a more detailed article on sequences
>to Builder.com. But a more interesting article might be one
>that explored various ways to automatically generate primary
>keys. So, in the name of research, let me throw out the
>following questions:
>
>What mechanisms have you used to generate primary keys?
>Which ones worked well, and why? Which mechanisms worked
>poorly?
>
>I've run up against the following approaches:
>
>* Hit a table that keeps a counter. This is the "roll your
>own sequence method". The one time I recall encountering
>this approach, I helped convert it over to using stored
>sequences. This was because of concurrency problems: with
>careful timing, two users could end up with the same ID
>number for different records. Is there ever a case when this
>roll-your-own approach makes sense, and is workable?
>
>* Stored sequences. I worked on one app that used a separate
>sequence for each automatically generated primary key. I
>worked on another app, a smaller one, that used the same
>sequence for more than one table. The only issue that I
>recall is that sometimes numbers would be skipped. But end
>users really didn't care, or even notice.
>
>* The SYS_GUID approach. I've never used SYS_GUID as a
>primary key generator. I wonder, was that Oracle's
>motivation for creating the function? Has anyone used it for
>primary keys in a production app? What's the real reason
>Oracle created this function?
>
>* Similar to SYS_GUID, I once worked on an obituary-tracking
>application that built up a primary key from, as best I can
>recall now: date of death, part of surname, part of first
>name, and a sequence number used only to resolve collisions,
>of which there were few. The approached worked well,
>actually, because whatever fields we munged together to
>generate a primary key gave us a unique key the vast
>majority of the time.
>
>The SYS_GUID approach is interesting, but if you need an ID
>number that users will see, and that users might type in
>themselves (e.g. social security number), is SYS_GUID really
>all that viable?
>
>Best regards,
>
>Jonathan Gennick --- Brighten the corner where you are
>http://Gennick.com * 906.387.1698 * mailto:jonathan@gennick.com
>
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