Re: Define "flatten database" ?

"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)
Received on Fri Jan 28 2005 - 16:55:28 CET