Re: Natural keys vs Aritficial Keys
Date: Sat, 16 May 2009 18:35:36 GMT
Message-ID: <YHDPl.1490$wR5.1128_at_nwrddc02.gnilink.net>
"Roy Hann" <specially_at_processed.almost.meat> wrote in message
news:VbWdnR8zmc-lHZPXnZ2dnUVZ8jWdnZ2d_at_pipex.net...
> Walter Mitty wrote:
>
>> I'm confused about some recent trends in database design.
>
> No you're not.
>
> [snip]
>
>> What I don't get is whether I've understood something that today's
>> trendsetters never learned or whether they are taking into consideration
>> matters that I never considered important, back in the day. I've read
>> their
>> arguments carefully, and it seems to me that failure to declare UNIQUE
>> and
>> NOT NULL constraints on the most widely used candidate keys is simply an
>> invitation to degradation of data integrity. PRIMARY KEY is a convenient
>> way to get those two constraints with one declaration.
>
> That misses the point. PRIMARY KEY and UNIQUE are supposed to prevent
> potentially contradictory facts. They have nothing to do with
> addressability. If RDBMSs or SQL DBMSs needed the concept of an
> address they would have it and it would be unique and you wouldn't
> have to everywhere repeatedly assert the most obvious property of an
> address is uniqueness.
>
> I think the urge to want to address rows is not just a hankering for
> network databases though. Programmers worry about what to do if a user
> mis-keys a natural key value which then gets propagated to a number of
> tables. If they have kept the natural key in one place it needs to be
> fixed in only one place. I've had quite good luck weening colleagues
> off spurious synthetic keys by encouraging them to declare their
> foreign keys with ON UPDATE CASCADE. (One or two demand benchmarks
> before they believe it is practically free, but generally they get it.)
> I suspect that it became established "best practice" to use
> synthetic keys everywhere back when few SQL DBMSs supported ON UPDATE
> CASCADE and it has just stayed with us.
>
>> Can some body explain to me what these people are thinking?
>
> They aren't.
>
> --
> Roy
>
Thanks for your response. You are another regular whose responses often provide me with valuable insight.
Thanks again. Received on Sat May 16 2009 - 20:35:36 CEST