What is SQL

SQL means Structured Query Language. With help of SQL we can access and manipulate databases. SQL executes queries and receives data from a database. In SQL we can insert, update and delete records in a database. We can create new tables, views and stored procedures in a databases & can set permissions on these tables, procedures, and views.

How to use SQL for websites

For using SQL in our website we need to have a program like RDBMS Relational Database Management System like MS Access, MySQL, SQL Server plus a server side scripting language like ASP or PHP.  Also we must require basic knowledge of HTML & CSS.

The Data in RDBMS is stored in tables. SQL Language is not case sensitive.

SQL can be divided into two parts:

The Data Manipulation Language (DML) & Data Definition Language (DDL).

The query and update commands form the DML part of SQL:

SELECT - extracts data from a database.

UPDATE - updates data in a database.

DELETE - deletes data from a database.

INSERT INTO - inserts new data into a database.

The DDL part of SQL allows database tables to be created or deleted.

CREATE DATABASE - creates a new database.

ALTER DATABASE - modifies a database.

CREATE TABLE - creates a new table.

ALTER TABLE - modifies a table.

DROP TABLE - deletes a table.

CREATE INDEX - creates an index.

DROP INDEX - deletes an index.

Some Basic SQL Commands

The SQL SELECT statement extracts data from one or more database tables or views.

SELECT Colname1, Colname2, …
FROM Table1

The SQL INSERT INTO inserts new data to database :

INSERT INTO Country (State, People, Date)
VALUES ('MP', 20, '15/12/2006')

The SQL UPDATE updates data of database:

UPDATE Table1
SET Column1 = Value1, Column2 = Value2, …

The SQL DELETE deletes data from database.

DELETE FROM Country
WHERE People = 20

The SQL syntax for CREATE TABLE is

CREATE TABLE "NameofTable"
("column 1" "datatype",
"column 2" "datatype",
... )

for eg.

CREATE TABLE employee
(First_Name char(25),
Last_Name char(25),
Address char(25),
City char(25),
Country char(25),
.....