Database- SQL

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• SQL stands for structured Query Language. 
• SQL is an ANSI  (i.e. American National Standards Institute  ) standard computer language for accessing and manipulating database systems.
• SQl statements are used to retrieve and update data in a database.
• SQL works with database programs like MS Access ,DB2,Informix ,MS SQL Server, Oracle ,Sybase,etc.
• The first version ,initially called SEQUEL,was designed to manipulate and retrieve data 
• SQL is a Non - procedural query language.
• Sometimes referred to as a Database Gateway Language as an ANSI made it a standard language for all DBMS.

SQL commands are divided into following categories:-
1)Data Definition Language-
                   It uses create,alter,drop,truncate
2)Data Manipulation Language -
                   It uses insert ,update,delete
3)Data Query Language -
                   It uses select
4)Data Control Language
                   It uses grant ,revoke
5)Transaction control Language
                   It uses commit,rollback
Syntax:
Create-  CREATE TABLE tablename(columnname1 data_type (size)[constraints],(columname2 data_type (size)[constraints],....)

Alter- ALTER TABLE tableman ADD(<columnname> data_declaration[constraints],<columnname> data_declaration[constraints],.....);

 To delete  Drop - DROP TABLE <tablename>[CASCADE CONSTRAINTS];

Truncate Table<tablename>;
removes all rows from a table and is high speed data deletion statement.


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