An Introduction to SQL

Structured Query Language (SQL) is an open standard that has been maintained by the American National Standards Institute (ANSI) since 1986. A major revision of the SQL standard, SQL2, was released in 1992.

Also the version, SQL3 contains object-oriented components.The SQL language is essentially a programming language for relational databases and is independent of the underlying database structure. Today, SQL is one of the most widely used cross−vendor languages. Many relational database management systems (RDBMS) support SQL language and if you know how to use it, you can create database applications in MySQL, MS SQL Server, DB2, Oracle, PostgreSQL, and other relational database management systems. SQL stores data in objects which have been created with relations among them.  The database objects in its main structure are tables which are indemnified for exclusive objects or for properties (attributes) of them. Thus, a database is a collection of tables and functions. A table is an array of two dimensions and each field of it (column of the table) represents an attribute of the object (entity) which the table concerns. On the other hand the horizontal structure of the table (rows) declares the data records which the table contains. Thus, a database table is a list of records (rows) which have the same structure and the same fixed number of fields (columns). Unfortunately, until now the SQL compatibility could not be achieved by RDBMS commercial database developers. ANSI SQL92 has been developed as a standard that should be followed by those who are going to create database systems supporting SQL. RDBMS developers in most of the cases in order to differentiate their systems are based on a different version of SQL implementation and do not implement fully ANSI SQL92–compatible SQL engines, adding their own different features and the database portability among different database systems is lost. You can visit the official site of ansi.org for further information about the ANSI SQL92 standard at: http://www.ansi.org.