I am looking in AdventureWorksDW2008R2 database. I looked at its fact tables, e.g., FactInternetSales I was expecting that it will have its primary key or at least I have a unique index on (ProductKey, OrderDateKey, DueDateKey, ShipDateKey, ) All the columns it has foreign keys on. But to my surprise it has primary key on [SalesOrderNumber] , [SalesOrderLineNumber]) 2. Similarly I see FACTSalesQuota has its primary key on SalesQuotaKey which is a surrogate key instead of DateKey, EmployeeKey I have read many artcles on internet, while Kimbals book recommends a primary key all the dim tables in its star schema, everyone does not follow this approach, why?? If in start schema there are many dim tables, primary key can be very long. If we do not have primary key on all dim keys, are there any performance implications because SQL Server optimzer does some optimizations based on start schema.

Hi Prem Mehrotra, The AdventureWorks DW database is mainly focus on demonstrates how to build a data warehouse, please refer to details about data warehouse design considerations: http://msdn.microsoft.com/en-us/library/aa902672(v=sql.80).aspx Thanks, Eileen Eileen Zhao TechNet Community Support