SQL

SQL is an ANSI (American National Standards Institute) standard but there are many different versions of the SQL language.

What is SQL?

SQL is structured Query Language which is a computer language for storing, manipulating and retrieving data stored in relational database.

SQL is the standard language for Relation Database System. All relational database management systems like MySQL, MS Access, Oracle, Sybase, Informix, postgres and SQL Server uses SQL as standard database language.

Also they are using different dialects, Such as:

• MS SQL Server using T-SQL,
• Oracle using PL/SQL,
• MS Access version of SQL is called JET SQL (native format )etc

Why SQL?

• Allow users to access data in relational database management systems.
• Allow users to describe the data.
• Allow users to define the data in database and manipulate that data.
• Allow to embed within other languages using SQL modules, libraries & pre-compilers.
• Allow users to create and drop databases and tables.
• Allow users to create view, stored procedure, functions in a database.
• Allow users to set permissions on tables, procedures, and views

History:

• 1970 -- Dr. E.F. "Ted" of IBM is known as the father of relational databases. He described a relational model for databases.
• 1974 -- Structured Query Language appeared.
• 1978 -- IBM worked to develop Codd's ideas and released a product named System/R.
• 1986 -- IBM developed the first prototype of relational database and standardized by ANSI. The first relational database was released by Relational Software and its later becoming Oracle.

SQL Process:

When you are executing an SQL command for any RDBMS, the system determines the best way to carry out your request and SQL engine figures out how to interpret the task.

There are various components included in the process. These components are Query Dispatcher, Optimization engines, Classic Query Engine and SQL query engine etc. Classic query engine handles all non-SQL queries but SQL query engine won't handle logical files.

Following is a simple digram showing SQL Architecture: