Databases are designed, built, and populated with data for a specific purpose and for an intended group of users. Databases help people keep track of things. For example, one's school probably has a database with information about its students—name, identification number, address, year in school, grade point average, and so on. These data are used by the school administration to keep track of how many students are enrolled in the school and to plan how many and what kinds of classes are needed for these students. Databases like this one (called SCHOOL here) are designed, built, maintained, and queried using a set of tools called a database management system (DBMS). The most common language used with DBMS is called SQL.

SQL (Structured Query Language) is the set of instructions used to define and manipulate data in many relational databases. Some people pronounce SQL...