- 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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