adding to what i said on a serious note you acn have alook at denormalization in by running the script sh_mail.sql which creates the datawarehouse schema and the following atbles

Table Number of Rows
customers 50.000
countries 19
products 10.000
sales 1.016.271
times 1461
promotions 500
channels 5

script is supplied with oarcle 9i (i am not sure about 8i though)

hope this helps

hrishikesh