SQL Introduction

SQL Introduction

Structured Query Language (SQL) is a Command based non procedural standard language for operating databases. SQL follows ANSI standards.
SQL Creates New Databases, Inserts Records, Updates Records and can delete records.
Using SQL, we can set permissions for Tables, Procedures and Views.

There are so many different versions of SQL available in the IT industry, but all are support SELECT, UPDATE, DELETE, INSERT, WHERE Commands.

Usage of SQL in Web Applications

If we want use database in web applications, below things are required:
  • A Database Management System (either MS Access or SQL Server or Oracle or Sybase or MySQL etc…)
  • A server-side scripting language, like PHP or ASP or JSP
  • SQL
  • HTML / DHTML/ CSS
Data
Information that can be stored, organized and used in the computer system

Generally data has two formats; one is File Format another Table Format. Table format is powerful and useful format, where as File format has organization.


Database

A Collection of meaningful Information stored, organized and Managed in the Computer System.

DBMS
It is a collection of interrelated data and a set of programs to access and modify the data.

RDBMS

RDBMS stands for Relational Database Management System.
RDBMS is the basis for SQL, and for all modern database systems like MS SQL Server, IBM DB2, Oracle, and MySQL.
The data in RDBMS is stored in database objects called tables.
A table is a collection of related data entries and it consists of columns and rows.

Tables

A database contains one or more tables. Each table is identified by a name (e.g. "Employee" or "Cities"). Tables contain records (rows and columns) with data.
an example of a table called "Employee":
EMP_ID
FirstName
LastName
Address
Qualification
Pro-001
Chandra Mohan
Reddy
Hyderabad
MCA
Pro-002
Sunil
Duggal
Mumbai
BTech
Pro-003
Ananth
Varma
Vizag
BTech
The table above contains three records (3 rows and 5 columns)

SQL Statements

Most of the Operations on a Database can be performed using SQL Statements

Ex:
Using the following SQL Statement we can select all records from the Employee Table.

Select * From Employee

Note: SQL is not a case sensitive language, we can use either upper case or lower case letters.

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