Practical SQL, 2nd Edition

7 Joining Tables in a Relational Database

In Chapter 2, I introduced the concept of a relational database, an application that supports data stored across multiple, related tables. In a relational model, each table typically holds data on a single entity—such as students, cars, purchases, houses—and each row in the table describes one of those entities. A process known as a table join allows us to link rows in one table to rows in other tables.

The concept of relational databases came from the British computer scientist Edgar F. Codd. While working for IBM in 1970, he published a paper called “A Relational Model of Data for Large Shared ...