Welcome Guest
New User? Register | Login

Tutorials

SQL

IT Tags

DiigIT » SQL » Tutorials

Post your Article

Database Management System

Subscribe in a reader

By: rekha singh | 29 Apr 2010 12:18 pm

Database Management System

Database management system are used when large quantities of data that needs to be tracked in an organization. Classical paper based data management systems cause inefficient retrieval and in accurate storage of valuable data.
A database is an organized collection of data provides you with the software tool you need to organize and access that data in a flexible manner.

DBMS example

Access - Microsoft
DB/2 - IBM
Informix
MS SQL Server
MySQL - open source etc....
It include facilities to add, modify or delete data from the database, ask questions (or queries) about the data stored in the database and produce reports summarizing selected contents.

Tables

Tables comprise the fundamental building blocks of any database.
A table column is referred as a field which represents different characteristics of stored data.
Table Row is referred as a record which represents individual data items.
Each record is identified using a unique field called a Primary key.

Queries

Queries are used to retrieve data from the database as required.
Queries are written using a language called Structured Query Language (SQL).
SQL dwfines the methods used to create and manipulate relational databases on all major platforms.
SQL comes in many flavors. Oracle databases utilize their proprietary PL/SQL. Microsoft SQL Server makes use of Transact-SQL. However, all of these variations are based upon the industry standard ANSI SQL.

Structured Query Language

SQL commands can be divided into two main sub languages.
The Data Definition Language (DDL) contains the commands used to create and destroy databases and database objects. (Tables, Procedures) etc...
After the database structure is defined with DDL, database administrators and users can utilize the Data Manipulation Language to insert, retrieve and modify the data contained within it.

Data Definition Language

Create statement.
This statement is mainly used for creating databases and tables
e.g. 1 To create a database payroll

create database payroll

e.g. 2 To create a table employee with following fields

Field Name Data Type

Empid Integer

Empname Text

Age Integer

Salary integer

create table employee (Empid int,Empname varchar(50), age int, salary int);

USE

USE Statement is used to select a database from the list of database management system.

e.g. we want to select payroll database

USE payroll;

Drop

DROP statement is used to remove a database / table/ procedure from the database available in database management system.

Data Manipulation Language (DML)

The data Manipulation Language (DML) is used to retrieve, insert and modify database information.
INSERT

Insert statement is used to insert records into a database.

e.g. To insert a record into the above created table employee

insert into employee values (001,'Saman Silva', 34,12000);

SELECT

Allow database users to retrieve the specific information they desire from an operational database. Consider the above create table with sample data

Empid Empname Age Salary

001 Saman Silva 34 12000

002 Kamal Perera 30 20000

003 Mala Fernando 26 10000

Retrieve all the records

select * from employee

Retrieve employees whose salary is greater than 15000

select * from employee where salary>15000

Find the employee name whose empid is 003

select empname from employee where empid=003

Comments

No Comments Posted for this Article.

Database Management System

Comments

Leave a comment