History of SQL
In 1970, Dr. E.F. Codd published “A Relational Model of Data for Large Shared Data Banks,” an article that outlined a model for storing and manipulating data using tables. Shortly after Codd’s article was published, IBM began working on creating a relational database. Between 1979 and 1982, Oracle (then Relational Software, Inc.), Relational Technology, Inc. (later acquired by Computer Associates), and IBM all put out commercial relational databases, and by 1986 they all were using SQL as the data query language.
In 1986, the American National Standards Institute (ANSI) standardized SQL. This standard was updated in 1989, in 1992 (called SQL2), and again in 1999 (called SQL3). Standard SQL is sometimes called ANSI SQL or SQL92. All major relational databases support this standard but each has its own proprietary extensions. Unless otherwise noted, the SQL taught in this course is the standard ANSI 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
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.
Following is a simple digram showing SQL Architecture:
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.