On Feb 27, 8:42 am, "Adrian Maier" <[EMAIL PROTECTED]> wrote:
> On 2/27/07, Langdon Stevenson <[EMAIL PROTECTED]> wrote:
>
>
>
> > My understanding is that Cake 1.1.x.x doesn't support multi-column keys.
>
> > This feature request in track:https://trac.cakephp.org/ticket/1293
> > indicates that the priority for this feature is very low and unlikely to
> > be implemented.
>
> > Are you working with a legacy database? Or is this your preferred way
> > of building the primary key?
>
> Is this still true for Cake 1.2.x.x ?
>
> You might find this article interesting. It is about surrogate primary
> key ( 'id' - integer )
> which are sometimes convenient (from a performance point of view) but
> are in fact
> an evil compromise because such a primary key *does* allow row duplicates :
Does it? I always thought not including a unique index on a table's
data allowed duplicates.
And I feel that's all the article proves. The PK is for identifying a
row of data, a unique index is for preventing duplicates. There are
times when the two can be one and the same, but in most cases they
should not - if only because choosing something that seems to be
unique which turns out not to be, or in some cases is null, is so
difficult to rectify (quickly).
What does this mean (extract from comments by the article author
regarding one of the examples of why surrogate keys are bad):
"You're correct, though, that because of the size of the key (three
columns, one of them up to 100 chars of text) the table carried an
INT4 surrogate key which is what we used for joins and application
logic"
My take is "the table had a normal PK", and kind of reinforces /why/ a
numeric unique id field is used and useful as a prmiary key, and /why/
a unique index on a table's data doesn't and shouldn't serve the same
purpose.
All IMO of course :),
AD
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