Optimizing SQL Server Database Design

When designing columns to store formatted data, such as Social Security numbers or phone numbers, you have two choices. You can choose to store the data with no formatting or with formatting. Each choice has its pros and cons. If you store the data with formatting, then your disk space requirements will be slightly higher than if you don't store the data with formatting. If you store the data without formatting, then you will have to add or remove formatting each time you INSERT or UPDATE a record, which adds to CPU and memory overhead on the server. In other words, the choice you make affects your server's load.
Which option you should choose in order to maximize performance is not always obvious, but many database designers choose to store formatted data because they feel the savings in CPU time and memory overhead (because formatting isn't performed on the fly) is more important than saving some space on the disk drive. You will have to examine your application closely to determine, in your particular case, which option will save your application the most overhead. [6.5, 7.0, 2000, 2005]