Re: Define "flatten database" ?
Date: Fri, 28 Jan 2005 16:18:06 -0800
Message-ID: <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)
Received on Sat Jan 29 2005 - 01:18:06 CET