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Denormalized columns [message #208895] Tue, 12 December 2006 08:08 Go to next message
gajini
Messages: 259
Registered: January 2006
Senior Member
Hi,

what is meant by denormalized columns?
When it's required/when we'll create it & how the values for these columns are obtained?

Can anyone explain this concept with an example?

Thanks,
Gajini
Re: Denormalized columns [message #208930 is a reply to message #208895] Tue, 12 December 2006 11:21 Go to previous messageGo to next message
dba_blr
Messages: 43
Registered: December 2006
Member
Denormalized columns are used mostly in DWH environments. To be more specific the Fact tables are mostly denormalized ones.

It helps in reducing resource contention.

These are generally populated using ETL process.
Re: Denormalized columns [message #208969 is a reply to message #208930] Tue, 12 December 2006 15:26 Go to previous message
andrew again
Messages: 2577
Registered: March 2000
Senior Member
http://www.dmreview.com/article_sub.cfm?articleID=5337

You should have a complete understanding of the real benefits and real disadvantages of denormalized structures before using them. You can denormalize from a parent table onto a child table (say to record a State on an address table), from the current table onto itself (e.g. price + tax = total) or from a child table onto a parent table (e.g. order table has a Total column based on child records).
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