data warehousing

what is this data warehousing?

what actually they doin this,what languages are needed for this..i want complete information on this..plz refer me to some good link,i cant find one

Praveen,
Check out these sites:
http://www.datawarehouse.com/home/

Praveen,
Check out these sites:
http://www.datawarehouse.com/home/ http://www.cio.com/research/data/
This one will give you the basic run down:

http://www.kenorrinst.com/dwpaper.html