What Is a Relational Database?

SQL Server is a database management server that creates and maintains relational databases. Unfortunately, the term relational database is one of the most used and abused buzzwords in the computer business. The term has at least three meanings. A relational database can be:

• A database in which data is stored in tables: In a relational database, groups of similar records are called tables. A database usually consists of more than one table - in fact, it isn't uncommon for a single database to have dozens of different tables. You can establish relationships between and among these tables based on common information. For example, a sales database might contain a table of customer information and a table of invoices, with both tables containing a customer number column that establishes a relationship between the tables.
• A database model based on a Conehead branch of mathematics called Set Theory: This is actually the most technically precise definition of a relational database, but only computer geeks know or care. Contrary to popular belief, the term relational database is not derived from the ability to create relationships among tables, but from the term relation, a mathematical term that refers to the way data is arranged into tables of rows and columns.
• A database that's accessed via SQL: SQL, which stands for Structured Query Language, provides a practical way to access data stored in relational tables. A database that's based on SQL is inherently relational because SQL stores its data in tables and is based on Set Theory. SQL Server, as its name implies, is based on SQL.

From a practical point of view, the third definition is the most important: A relational database is a database that you can access via SQL. Thus, SQL Server is used for relational databases. The next section dives a little more deeply into what SQL is.