Although most successful databases are normalized to some degree, there is one substantial drawback of a normalized database: reduced database performance. The acceptance of reduced performance requires the knowledge that when a query or transaction request is sent to the database, there are factors involved, such as CPU usage, memory usage, and input/output (I/O). To make a long story short, a normalized database requires much more CPU, memory, and I/O to process transactions and database queries than does a denormalized database. A normalized database must locate the requested tables and then join the data from the tables to either get the requested information or to process the desired data. A more in-depth discussion concerning database performance occurs in Hour 18, "Managing Database Users."
