Overview of SQL
SQL (Structured Query Language) is a programming language designed for managing data in relational database management systems (RDBMS).
Originally based upon relational algebra and tuple relational 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". Despite not adhering to the relational model as described by Codd, it became the most widely used database language.
Basic SQL is grouped into three sub-languages:-
- Data Definition Language (DDL)
- Creating the database and database objects such as tables, views and triggers.
- Data Control Language (DCL)
- Granting users access to different databases, tables, views and other database objects.
- Data Manipulation Language (DML)
- Inserting, updating, deleting and selecting data from tables in the database.
SQL is designed for a specific purpose: to query data contained in a relational database. SQL is a set-based, declarative query language, not an imperative language such as C or BASIC. However, there are extensions to Standard SQL which add procedural programming language functionality, such as control-of-flow constructs.
Sources
Wikipedia contributors. "SQL." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 10 Sep. 2011. Web. 12 Sep. 2011.