Data Warehouse Newbie Questions

I have came to the conclusion that I need a "Data Warehouse" ; I have read some papers, and still have a few questions on the subject :

1. Suppose I have a 'Sales' "fact table"... some Sales are "basic sales", but some are more complicated, hence I need to store more "attributes". Do I create a new 'Special Sales' "fact table" ? Or is it better that
   'Sales' table holds all the possible attributes, and have them "NULL"
   when not relevant ? And what about using the "supertype" pattern ( a special sale is described by a record in 'Sales' table and a record in
   'Special Sales' that provides the additional attributes ) ?
   ([ this question relates to one of my previous posts -- and I thank people who took time to answer me --, but I would like people's opinion in the context of a data warehouse, that will contain up to 200 million records ! ])
2. In a 'Time' dimension, each day, with its week, month, year, etc must be entered in the corresponding table. Who does this process ? Is it done automatically by some kind of mechanism in the RDMS or must it be done manually ?
3. Does data REALLY need to be denormalised (I am a newbie !) ? Is it necessary or is it just a hacker optimisation ? I have allways been taught to normalise !
4. Do you know of any good web sites on the subject of designing a Data Warehouse ?

Thanks in Advance for your answers !!

SerGioGio Received on Tue Jun 04 2002 - 15:36:37 CEST