Databases consist of a number of tables, each table holding a set of related data. Databases may also contain stored procedures which contain instructions for manipulating that data. Although stored procedures have advantages, they are not necessary for most Web sites because those instruction can be embedded in server-side scripting. If you need a database at all, however, you cannot get by without the tables.

Databases may contain any desired type of data, but some common types are as follows:

• Login and session information for individual users
• Information associated with items for sale
• Customer histories
• Order tracking information
• Information to control the structure and display of the Web site itself. For example, this site uses tables to generate the menu bar to the left. The Site Map page is created from the same table.

There is a lot involved in creating a proper database design. For optimal performance and usefulness, it should be normalized and doing so is not for the faint of heart. Although we take care of that for you, we have included the rules for the five levels of normalization here.