Difference between revisions of "SQL Overview"

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SQL stands for Structured Query Language. This is a semi-mathematical method of asking
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questions about information in a database, especially when the database has a relational view.
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SQL stands for Structured Query Language. It is an ANSI/ISO standard language for querying and otherwise working with [[relational database]]s. Although there is a standard for SQL, database vendors typically implement slightly different variants of the language (e.g., in terms of the data tpes supported). In addition, vendors often add procedural extensions to the language (e.g., PL/SQL for Oracle or Transact-SQL for SQL server).
  
 
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Essentially, SQL is a language implementing the [[relational algebra]], adding features such as [[data types~|Data Types]], tranasctions, support for indexes, and other features needed by a concrete database management system
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Latest revision as of 17:57, 28 February 2012

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SQL stands for Structured Query Language. It is an ANSI/ISO standard language for querying and otherwise working with relational databases. Although there is a standard for SQL, database vendors typically implement slightly different variants of the language (e.g., in terms of the data tpes supported). In addition, vendors often add procedural extensions to the language (e.g., PL/SQL for Oracle or Transact-SQL for SQL server).

Essentially, SQL is a language implementing the relational algebra, adding features such as Data Types, tranasctions, support for indexes, and other features needed by a concrete database management system