Beginning Microsoft® SQL Server® 2008 Programming

Chapter 1. RDBMS Basics: What Makes Up a SQL Server Database?

What makes up a database? Data for sure. (What use is a database that doesn't store anything?) But a Relational Database Management System (RDBMS) is actually much more than data. Today's advanced RDBMSs not only store your data, they also manage that data for you, restricting the kind of data that can go into the system, and facilitating getting data out of the system. If all you want is to tuck the data away somewhere safe, you could use just about any data storage system. RDBMSs allow you to go beyond the storage of the data into the realm of defining what that data should look like, or the business rules of the data.

Don't confuse what I'm calling the "business rules of data" with the more generalized business rules that drive your entire system (for example, preventing someone from seeing anything until they've logged in, or automatically adjusting the current period in an accounting system on the first of the month). Those types of rules can be enforced at virtually any level of the system (these days, it's usually in the middle or client tier of an n-tier system). Instead, what we're talking about here are the business rules that specifically relate to the data. For example, you can't have a sales order with a negative amount. With an RDBMS, we can incorporate these rules right into the integrity of the database itself.

The notion of the database taking responsibility for the data within, as well as the best methods ...