Re: Traversing large data table

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: Louis Davidson (dr_dontspamme_sql_at_hotmail.com)
Date: 11/03/04 

Date: Tue, 2 Nov 2004 23:57:46 -0600

> a quote from Dr. Codd: "..Database users may cause the system to
> generate or delete a surrogate, but they have no control over its value,
> nor is its value ever displayed to them ..."(Dr. Codd in ACM TODS, pp

> Sounds pretty clear to me. What part of "no control over" and "nor ever
> displayed" did I miss?

Ok, I think I understand what we are talking about here. I have always
considered "nor ever displayed" to be a logical thing, not a physical thing.
As in they could be seen by administrators, but not by users. I see that
this could be, and probably is more correct to be, never displayed in that
it is completely inaccessible.

I will just ignore the obvious evils of pointer math in a set based
language, since none of us is going to disput that.

Reseeding them is bad, but based on the original laws, things like DBCC
shouldn't need to exist, but because of the realities of hardware and
software failures, we have to have tools to work on the physical level
occasionally. There is seldom a need to reseed an identity anymore, but it
does happen occasionally. 

-- 
----------------------------------------------------------------------------
Louis Davidson - drsql@hotmail.com
SQL Server MVP
Compass Technology Management - www.compass.net
Pro SQL Server 2000 Database Design -
http://www.apress.com/book/bookDisplay.html?bID=266
Note: Please reply to the newsgroups only unless you are interested in
consulting services.  All other replies may be ignored :)
"Joe Celko" <jcelko212@earthlink.net> wrote in message
news:ey5a9jSwEHA.3844@TK2MSFTNGP09.phx.gbl...
> a quote from Dr. Codd: "..Database users may cause the system to
> generate or delete a surrogate, but they have no control over its value,
> nor is its value ever displayed to them ..."(Dr. Codd in ACM TODS, pp
> 409-410) and Codd, E. (1979), Extending the database relational model to
> capture more meaning.  ACM Transactions on Database Systems, 4(4).  pp.
> 397-434.
>
> Sounds pretty clear to me. What part of "no control over" and "nor ever
> displayed" did I miss?
>
> To me this means that a surrogate ought to act like an index; created by
> the user, managed by the system and NEVER seen by a user.  For example,
> Sybase SQL Anywhere does a nice job of building pointer chains to
> co-ordinate PK-FK relationships and cascade their DRI actions, but you
> do not get to do pointer arithmetic, re-seed them or anything else like
> you do in T-SQL.
>
> --CELKO--
> Please post DDL, so that people do not have to guess what the keys,
> constraints, Declarative Referential Integrity, datatypes, etc. in your
> schema are. Sample data is also a good idea, along with clear
> specifications.
>
>
> *** Sent via Developersdex http://www.developersdex.com ***
> Don't just participate in USENET...get rewarded for it!

Relevant Pages

  • Re: Traversing large data table
    ... "..Database users may cause the system to ... nor is its value ever displayed to them ..."(Dr. Codd in ACM TODS, ... What part of "no control over" and "nor ever ... To me this means that a surrogate ought to act like an index; ...
    (microsoft.public.sqlserver.programming)
  • Re: Database design, Keys and some other things
    ... "..Database users may cause the system to generate or delete ... > a surrogate, but they have no control over its value, nor is its value ... > ever displayed to them ..."(Dr. Codd in ACM TODS, pp 409-410) and Codd, ...
    (comp.databases.theory)
  • Re: Guidelines to a decent support of surrogate key implementation
    ... totally unrelated to the logical data model. ... A surrogate key is system generated to replace the actual key ... with a quote from Dr. Codd: ... Extending the database relational model to capture more meaning. ...
    (comp.databases.theory)
  • Re: [NOW ANSWER Aarons QUESTION CELKO]
    ... True surrogates are fine; ... surrogate keys Dr. Codd was refering to when he wrote: ... Codd in ACM TODS, pp 409-410) and Codd, E., Extending the ... database relational model to capture more meaning. ...
    (microsoft.public.sqlserver.programming)
  • Re: Negative Numbers in "Identity" or" Autonumber" fields
    ... WHAT IS A SURROGATE KEY? ... A quote from Dr. Codd: "..Database users may cause the system to ... "There are three difficulties in employing user-controlled keys as ...
    (comp.databases.theory)