The final element of the application is the SQL Server database. This is the store for all the persistent objects the application uses.
In many Web applications, development starts with the database. In our case, the database is simply a store for persistent objects, so its structure was determined by the needs of the persistent objects. There is a table for each class of persistent objects, with a column for each data member. Each table row represents a specific object.
As mentioned earlier, each persistent object class provides a primary key field to enable each object to be uniquely identified. In the database, these fields are implemented as identity columns so that when new persistent objects are created, they will be assigned a unique primary key value.