SQL Overview
SQL is a programming language for Relational Databases. It is designed over relational algebra
and tuple relational calculus. SQL comes as a package with all major distributions of RDBMS.
SQL comprises both data definition and data manipulation languages. Using the data definition
properties of SQL, one can design and modify database schema whereas data manipulation
properties allows SQL to store and retrieve data from database.
Data definition Language
SQL uses the following set of commands to define database schema:
CREATE
Creates new databases, tables and views from RDBMS
For example:
Create database tutorialspoint;
Create table article;
Create view for_students;
DROP
Drop commands deletes views, tables and databases from RDBMS
Drop object_type object_name;
Drop database tutorialspoint;
Drop table article;
Drop view for_students;
ALTER
Modifies database schema.
Alter object_type object_name parameters;
for example:
Alter table article add subject varchar;
This command adds an attribute in relation article with name subject of string type.
Alter table article drop subject;
This command drops an attribute in relation article with name subject.
Data Manipulation Language
SQL is equipped with data manipulation language. DML modifies the database instance by
inserting, updating and deleting its data. DML is responsible for all data modification in databases.
SQL contains the following set of command in DML section:
SELECT/FROM/WHERE
INSERT INTO/VALUES
UPDATE/SET/WHERE
