What is SQL?
SQL Stands for Structured Query Language. It is pronounced as “sequel”. SQL is a computer language which is designed to get a information from database. It is used for storing, manipulation and retrieving data from database.
SQL was developed at IBM by Donald D. Chamberlin and Raymond F. Boyce in 1970s. This version is called “SEQUEL”. In 1974 SQL appeared and in 1979 Relational software released a first commercial product called System/R.
After that IBM starts developing commercial products based on the prototype of System/R.
- It allows users to extract data from relational database.
- It allows to create database and tables.
- It allows updating, inserting, deleting and altering database and tables.
- It provide security and allow to set a permission.
- Allows people to handle data in new ways.
DDL stands for Data Definition Language. It modifies the actual structure of the database rather than content of the database. The commonly used DDL commands are CREATE, DROP and ALTER.
CREATE TABLE – It creates a new table.
DROP TABLE – It deletes the ENTIRE table.
ALTER TABLE – Modifies the existing table.
DML stands for Data Manipulation Language. It modifies the content of a database. The commonly used DML commands are SELECT, INSERT, UPDATE, DELETE.
SELECT – Retrieve information from database.
INSERT – Add new information to a database.
UPDATE – Modifies the information currently stored in a database.
DELETE – Delete information from the database.