Sean Lange (7/29/2014)
Actually normalization (more tables) causes slower performance.
"It Depends". 😉
If you have de-normalized table that looks like a spreadsheet with date columns in it, queries can be both difficult to write and very slow in performance. "Normalizing" such a table to be more like an EAV table will allow for proper indexing, easy non-reporting style lookups-aggregations-etc, and still allow for some very high performance CrossTabs and Pivots for reporting purposes while also making it easier to create "moving window" reports.
--Jeff Moden
Change is inevitable... Change for the better is not.