Point 3: create a combined primary key out of two or more columns the
combination of which is always unique.
Alex
----- Original Message -----
From: <charles arehart <[EMAIL PROTECTED]>>
To: "SQL" <[EMAIL PROTECTED]>
Sent: Friday, January 04, 2002 4:44 AM
Subject: RE: Questions
> I'm not sure I agree with the "always use a manual numbering scheme".
While
> the case of portability is a worthy one, it's not a critical design factor
> for all db applications.
>
> Now, you may ask why not have the benefit anyway if it's as easy as you
> suggest in step 3 ("Create a new table, and then assign a unique value to
> it. You can do this in CF. Just loop through the table and add a new
number
> each time.") Do you really mean to suggest one should "loop through the
> table" to get a new id?
>
> Also, in a high-volume application, what are you doing to ensure that you
> don't inadvertently get the same new value from two threads running this
> code at the same time? If you're relying on the database to handle the
> concurrency issue, then you'd better indicate which isolation level you
> expect the dbms to support, and then use a CFTRANSACTION to indicate that
> around the process of finding the current high value and assigning the
next
> high value.
>
> I'd appreciate hearing your thoughts on these things. There are always
> tradeoffs in design decisions. I realize that not all apps will be
> high-volume enough to worry about this issue, but then again it's no less
> worthy a design factor than portability. It seems both subjects should be
> considered in debating CTLoo's question.
>
> /charlie
>
> -----Original Message-----
> From: Bruce Sorge [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, January 03, 2002 10:25 PM
> To: SQL
> Subject: Re: Questions
>
>
> ----- Original Message -----
> From: "CT, Loo" <[EMAIL PROTECTED]>
> To: "SQL" <[EMAIL PROTECTED]>
> Sent: Thursday, January 03, 2002 9:18 PM
> Subject: Questions
>
>
> > Dear SQL gurus,
> >
> > I have some questions on database design and hope all experts out there
> > can give me some ideas/advice.
> > Please advise/comment on the followings:-
> >
> > 1. Should one use the identity field as primary key in designing a
> > database?
> No. You should always use a manual numbering scheme, basically because, if
> ever you have to move this DB to another DB, even of the same type, and it
> is a truely relational DB, and you have ever deleted records (which I hear
> happens on occassion), you will have a lot of work ahead of you ensuring
> that all of the related tables are numbered correctly.
> > If yes, isn't it has a limitation when the number reaches its
> > limits?
> > 2. What would happens to the database when the identity field's value
> > reaches its limits?
> Another reason to use a manual numbering scheme.
>
> > 3. Any advice on selecting a primary key for a table where none of the
> > columns has unique value?
> Create a new table, and then assign a unique value to it. You can do this
in
> CF. Just loop through the table and add a new number each time.
> >
> >
> >
> > Thanks in advance.
> >
> > Kind regards,
> > CTLoo
> >
> >
> >
>
>
______________________________________________________________________
This list and all House of Fusion resources hosted by CFHosting.com. The place for
dependable ColdFusion Hosting.
Archives: http://www.mail-archive.com/[email protected]/
Unsubscribe: http://www.houseoffusion.com/index.cfm?sidebar=lists
