A Brief History of Databases
A little background on the evolution of databases and database theory will help you understand the workings of SQL. Database systems store data in every conceivable business environment. From large tracking databases such as airline reservation systems to a child's baseball card collection, database systems store and distribute the data that you depend on. Until the last few years, large database systems could be run only on large mainframe computers. These machines were traditionally expensive to design, purchase, and maintain. However, today's generation of powerful, inexpensive workstation computers enables programmers to design software that maintains and distributes data quickly and inexpensively.