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SQL INTRODUCTION 1 2 3 4 5

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Introduction to SQL Brief History SQL Standardization SQL Syntax Some Popular SQL Database Vendors

1.Introduction to SQL SQL (pronounced as Sequel; Structured Query Language) is a standard language for accessing and managing data held in RDMS (Relational Database Management Systems). It is originally based upon the relational algebra. It consists of data definition language and data manipulation language.

2.Brief History SQL was first developed at IBM by Donald D. Chamberlain, Donald C. Messerly, and Raymond F. Boyce in the early 1970's based on the Edgar F Codd's relational model. It was initially called the SEQUEL(Structured English Query Language) and was used for the manipulating and retrieval of data stored in IBM's original quasi-relational database management system, System R. The acronym SEQUEL was later changed to SQL because "SEQUEL" was a trademark of UK based Hawker Siddeley Aircraft Company.

3.SQL Standardization SQL became the standard of American National Standards Institute(ANSI) in 1986 and of International Organization for Standardization(ISO) in 1987. Most SQL Database vendors have their own proprietary extension in addition to SQL Standard. To maintain SQL compliance they all support major commands like (SELECT, INSERT, UPDATE, DELETE AND WHERE) in similar manner. Some standards and commands and extensions supported in one vendor might not be supported in another Vendor. So SQL is not fully compatible among different vendors and some features are vendor based like (Procedural Language Support, Triggers, Cursor, Functions etc). Get More Lecture notes and Computer Science Study Kit Android app from: http://computer-science-study-kit.blogspot.in/


SQL INTRODUCTION 4.SQL Syntax The SQL Syntax is almost same across different vendors but some database have different syntax. Like Some database, system requires semicolon (;) at the end of SQL statement. This is a standard way to separate SQL Statements. SQL is not CASE-sensitive. So command meanings are not changed if it is uppercase or lowercase. Example:

SELECT * FROM Contacts where SELECT , FROM are SQL commands. if they are written as

select * from contacts Their meaning remains the same.

5. Some Popular SQL Database Vendors        

Oracle Database Microsoft SQL Server MySQL IBM DB2 IBM Informix PostgreSQL Sybase Teradata

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Introduction To SQL