SQL stands for Structured Query Language. SQL is a tool for database management that provides function like organizing, managing and retrieving data stored in computer memory in the form of database. The SQL is pronounced as ‘sequel’. SQL is a language that interacts with database by performing requested function. SQL performs all these functions on a specific type of database called Relational Database. And the program that stores and manages all the information stored in the computer memory in the form of database is called Database Management System (DBMS).

Definition of SQL: “The process of requesting data from the database and retrieving back the results is called the structured query. “

Basic Functions of SQL

SQL functionality is similar to database management systems to control the data stored in the computer database:

1. Data Management Functions:

• Data Definition: Structure and organization can be defined using SQL. You an also create well defined relational structure of database.
  
  
• Data Manipulation: You can add, modify or delete the data items using SQL.
  
  
• Data Retrieval: SQL also allows you to request for data from the database and retrieve the required results.

2. Data Security Functions:

• Data Access: You can grant permission/authorization to the database users for accessing and manipulating the data stored using SQL.
  
  
• Data Sharing: SQL is used to share data between concurrent users without any conflict.
  
  
• Data Integrity: You can apply constraints to retain the database consistency while any alteration done to the database.

Basic SQL Commands for Data Manipulation:

SELECT : to retrieve data


INSERT : to insert new row


DELETE : to delete the rows from the database


UPDATE : to modify the existing data

SQL Commands for Data Definition:

CREATE TABLE : to add new table into the database


DROP TABLE : to delete a table from the database


ALTER TABLE : to modify the previous table structure


CREATE INDEX : to bind a new index with a column


DROP INDEX : to delete the index of column


CREATE VIEW : to add a view for database table


DROP VIEW : to delete the existing view of any table

Access Control Commands

GRANT : to grant access privileges to the database users


REVOKE : to remove access privileges from the database users

To retrieve the desired results from the requested SQL query some clauses are also used to filter the records from the results retrieved. Following are some clause commonly used to filter the results:

• WHERE
  
  
• FROM
  
  
• HAVING
  
  
• INTO