Re: Define "flatten database" ?

From: DA Morgan <damorgan_at_x.washington.edu>
Date: Sat, 29 Jan 2005 09:42:30 -0800
Message-ID: <1107020392.144332_at_yasure>

Alan wrote:

> "DA Morgan" <damorgan_at_x.washington.edu> wrote in message
> news:1106957734.316617_at_yasure...
>

>>Alan wrote:
>>
>>
>>>"Dawn M. Wolthuis" <dwolt_at_tincat-group.comREMOVE> wrote in message
>>>news:ctdn9o$7sq$1_at_news.netins.net...
>>>
>>>
>>>>"DA Morgan" <damorgan_at_x.washington.edu> wrote in message
>>>>news:1106859773.807419_at_yasure...
>>>>
>>>>
>>>>>silversw2000_at_yahoo.com wrote:
>>>>>
>>>>>
>>>>>
>>>>>>I had a database analyst interview yesterday on the phone, and the
>>>>>>interviewer brought up the phrase: "I flattened the database".
>>>>>>
>>>>>>I did not obfuscate in replying to her thread, but was able to avoid
>>>>>>having to know what she meant by that term.
>>>>>>
>>>>>>Can someone define "flatten database" for me, in 100 words or less (OK
>>>>>>500 words is fine).
>>>>>>
>>>>>>Fred Z.
>>>>>>
>>>>>
>>>>>Denormalize.
>>>>
>>>>I would guess "normalize" is more likely.  If the source dbms permits
>>>>non-1NF structures, then the term "flatten" is sometimes used to mean

>
> that
>

>>>>the data are put in1NF.  Terms I might use as synonyms to "flatten" are
>>>>"unnest", "explode", "normalize".  It isn't quite the same as

>
> normalizing,
>

>>>>however, because the embedded lists are not placed in a separate

>
> relation,
>

>>>>but rather the "scalar" data are repeated in each row, while the list

>
> has
>

>>>>one value per row.  Reasons to flatten the structure would include a

>
> need
>

>>>to
>>>
>>>
>>>>use a SQL-92-based tool or pour the data into a single Excel worksheet.
>>>>
>>>>If the source dbms is a SQL-based product, then the user might still be
>>>>dumping tag-delimited lists in as attribute values (we all know there

>
> are
>

>>>>people who do that, right?) or even using some non-1NF capabilities of

>
> the
>

>>>>particular RDBMS.
>>>>
>>>>Example:
>>>>
>>>>Start with:
>>>>
>>>>(12345,DeSmith,John,{jsmith_at_aol.com,JohnSmith_at_yahoo.com})
>>
>>>(23127,Meador,Beth,{beth_meador_at_msn.com,bmeador_at_hotmail.com,btm_at_ibm.org})
>>>
>>>>Then flatten it to get:
>>>>
>>>>(12345,DeSmith,John,jsmith_at_aol.com)
>>>>(12345,DeSmith,John,JohnSmith_at_yahoo.com)
>>>>(23127,Meador,Beth,beth_meador_at_msn.com)
>>>>(23127,Meador,Beth,bmeador_at_hotmail.com)
>>>>(23127,Meador,Beth,btm_at_ibm.org)
>>>>
>>>>That's my best guess.  --dawn
>>>>
>>>>
>>>>
>>>>>-- 
>>>>>Daniel A. Morgan
>>>>>University of Washington
>>>>>damorgan_at_x.washington.edu
>>>>>(replace 'x' with 'u' to respond)
>>>>
>>>>
>>>Dawn,
>>>
>>>Flattening is DEnormalizing. Period. You have it backwards and twisted.

>
> It
>

>>>could be called Neo-normalizing.
>>
>>Which part of reading comprehension did you miss?  ;-)
>>
>>My one word response was "Denormalize." You will find up up just
>>under the signature "Fred Z."
>>
>>So I'm not sure what it is you are responding to. And given that I
>>teach the subject here at the university I think I have at least
>>a basic knowledge thereof.
>>-- 
>>Daniel A. Morgan
>>University of Washington
>>damorgan_at_x.washington.edu
>>(replace 'x' with 'u' to respond)

>
>
> Geez, Dan, I was on your side. I was responding to Dawn's insitence that
> flattening was something other than denormalizing..

Sorry ... I've lost track of who said what when so please accept my sincere apology.

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)

Received on Sat Jan 29 2005 - 18:42:30 CET