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Chapter 1: Database DesignSQL Server is a relational database management system (RDBMS). In a relational database, data is stored in tables, each of which contains information about an object in the database. A table is a two-dimensional grid consisting of rows and columns, sometimes referred to as records and fields. A column or field contains data about some attribute of the object, such as the name of a customer, the color of a product, or the date of a sale. A row or record represents one instance of the object, such as a customer, an invoice, or a product.
In a relational database, there is no structure imposed on the data by the database or the database software. All the structure comes from the relationships you define between the tables. The relationships describe how the objects in the database interact. The relational database provides a set of tools to help you safeguard and maintain these relationships. For example, once you have defined the relationship between customers and invoices, the database can prevent you from deleting a customer who has an outstanding invoice.
A relational database also safeguards your data by employing transaction logging. This means that whenever a change is made to data stored in the database, the change is first written to a transaction log. Only then is the change made to the actual data. If the system were to crash during the change, SQL Server can complete or cancel the change entirely by referring to the transaction log. The data will never be left in an inconsistent state. As you develop applications in SQL Server 2000, keep in mind that how you program can impact the performance of the transaction log. Transaction loggingcannot be turned off-logging change is inherent to a relational database.
A Brief Summary Of The Development Of The Relational Da