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How to Normalize?
Message
De
15/02/2002 10:05:59
Lutz Scheffler (En ligne)
Lutz Scheffler Software Ingenieurbüro
Dresden, Allemagne
 
 
À
15/02/2002 09:43:40
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
00620634
Message ID:
00620654
Vues:
13
Hi Pete,

the idea on normalization is that instaed of write the same information over and over into a table you write it once in a 'lookup' table. The table where the information is needed POINTS to the respectiv record in the lookup table.


Think as adresses of your city.
if you write city, state, and so one line by line, city, state is repeated line by line. This needs space on your disk? If use a separeted table
put city, state in it and add in number this must be uniqe to this table.
So you need the space once

in the table holding adresses replace city, state with an number the same number as the one uniqe for city, state in lookup table. So you need less space.

And if somebody like to change city name only one record has to be changed.
(Ok it's rare changing city name, but think on Leningrad -> St'Petersburg or Karl-Marx-Stadt -> Chemnitz)

Also user can select out of lookuptable instead of entering citys name, state every time.

But do not over normalize, if you put each and every stuff in a lookup table user will hang programmer.

Or look above this lines. Forum und category are normalized ...

Agnes
>Hi all,
> I've read what I can find, downloaded an article, but I still can't quite get the hang of normalizing table(s). Every time I try, It's never quite the way the text(s) say it should be. I don't know how to check if I've gotten it right or wrong. Is there some sort of procedure that I haven't stumbled on? I'm working in FPW 2.6 under Win2K. Will eventually move to VFP7.
>
> Is there a definitive article or something that explains things fully for thick skulled people like me?
>
>Pete
Words are given to man to enable him to conceal his true feelings.
Charles Maurice de Talleyrand-Périgord

Weeks of programming can save you hours of planning.

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