Level of Normalization ?

Last Post 06 Jun 2006 07:39 AM by SQLUSA. 7 Replies.
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buchi_b
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16 Mar 2006 10:58 PM
Hi,

Can anyone suggest what is the best practical level of normalization that should be achieved under production environment.


mwesch
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17 Mar 2006 03:23 AM
3rd normal form is a practical goal.
buchi_b
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19 Mar 2006 11:06 PM
Hi Michael,

Thnks, but any reasons why we shouldn't go beyond that ?


GoldenGal
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05 Apr 2006 09:32 AM
No reason at all if the situation warrants it. This is a situation where you must look at each design decision individually.

Going beyond 3NF might cause addition multi-table join overhead on retrievals, which you have to balance against the problems inherent in data management (inserts, updates) of tables that are in anything less than 3NF, or even that qualify as 3NF.

SQL Server doesn't enforce any normal form (haven't we all seen 1NF, 2NF, even unnormalized data in production tables?), so you're pretty much free to do whatever you want to.

Good luck!
SQLUSA
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05 Apr 2006 11:27 PM
It depends Michelle.

It depends what shop you are working at.

In some installations 3NF+ is the norm, in others....well no NF at all...the rest in between.

It is good practice to keep the database in 3NF.

Most violations result from "percieved performance" considerations (too many joins...) or rush job environment.

Performance can be addressed many ways, "denormalization" (actually unnormalization) is the worst way of addressing it.

Kalman Toth, Database, Data Warehouse and BI Architect
http://www.sqlusa.com
The Best SQL Server 2005 Training in the World
cmdr_jpskywalker
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25 Apr 2006 12:53 PM
As they said, it depends on your business needs or what production environment you are supporting. Operational transactions/OLTP normally is in 3rd NF because of the average speed (single location) and reliability (no duplicate records to update). However, there are tables in 4th/5th form/BOYCE-CODD NF because of business requirement (ticket, passenger, airline) that is impractical for 3rd NF. If you are in data warehousing, then you might want to use DENORMALIZATION/INDEXING/REPLICATION to speed up/deploy reports to different business users.
sqladmin
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27 Apr 2006 09:44 AM
yes... this is true. there is such a thing as overnormalized.
getting beyond 4NF is a bit much.

good question though.

cheers
SQLUSA
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06 Jun 2006 07:39 AM
Actually in data warehousing the Star Schema, the basis for cube, is normalized.

However, reporting/staging tables are usually not normalized, and that is fine in a data warehouse.


Kalman Toth, Database, Data Warehouse and BI Architect
http://www.sqlusa.com
The Best SQL Server 2005 Training in the World




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