Often referred to as Structured Query Language, is a database computer language designed for managing data in relational database management systems (RDBMS), and originally based upon relational algebra and calculus. Its scope includes data insert, query, update and delete, schema creation and modification, and data access control. SQL was one of the first commercial languages for Edgar F. Codd's relational model, as described in his influential 1970 paper, “A Relational Model of Data for Large Shared Data Banks”. (from Wikipedia – http://en.wikipedia.org/wiki/SQL)
The web abounds with SQL tutorials and code snippets.