>What do the purists say? What do you people do in reality?

Design the "ideal" on paper; then denormalize, etc. for performance and practicality ... unless the DBA's run your IT department, in which case, you'll have to implement the ideal. :)

A distinction can be made between the "production" system and the "information" system.

The "production" system is highly normalized and is used primarily for OLTP (online transaction processing).

The "information" system feeds off the production system, may be denormalized, multi-dimensional and summarized to satisfy data warehouse/data mart needs and is geared towards OLAP (online analytical processing).

Each may use a different DBMS.