Introduction To DataBases

Introduction To Databases

This post is to give a basic introduction to databases by giving some definitions and explanations of some of the parts in a database and some types.
There is an accompanying podcast for this to assist you.

Definitions

Database:  Organized collection of logically related data.

Data: Stored representations of meaningful objects and events                                                                                            

- Structured: Numbers, text,dates.                                                                                                             

- Unstructured: images, video, documents

Information: Data processed to increase knowledge in the person using the data.

Metadata: Data that describes the properties and context of use data.

Graphical displays: Turns data into useful information that managers can use for decision making and interpretation.

The characteristics of Databases

·         The purpose of a database is to help people track things of interest to them.

·         Data is stored in tables, which have rows and columns like a spreadsheet. A database may have multiple tables, where each table stores data about a different thing.

·         Each row in the table stores data about an occurrence or instance of the thing of interest.

·         A database stores data and relationships.

·         Tables are related through Primary and foreign keys.

Why Use A Database?

·         The purpose of a database is to help people and organizations keep track of things.

·         Problems of using list to store data.

-Data inconsistencies

-Data Privacy: The departments want to store some, but not all, of their data.

Components of a Database system

·         User -- Database Application -- DBMS -- Database  (DBMS = Data Base Management System)

     -Create

     - Process

     - Administer

Components of a Database system with SQL

·         User -- Database Application –SQL-- DBMS – Database

       Create

     - Process

     - Administer

Applications, the DBMS, and SQL

·         Applications are the computer programs that users work with.

·         The Database Management System (DBMS) creates, Processes, and administers databases.

·         Structured Query Language (SQL) is an internationally recognized standard database language  that is used by all commercial DBMS.

Database Applications

·         Create and process forms

·         Process user queries

·         Create and process reports

·         Execute applications logic

·         Control application

The DBMS

·         Create database

·         Create tables

·         Create supporting structures(e.g. indexes)

·         Read database data

·         Modify (insert, update, or delete data)

·         Maintain database structures

·         Enforce rules

·         Control concurrency

·         Provide security

·         Perform backup and recovery

Database Contents

·         Tables of user data

·         Metadata

·         Indexes

·         Stored procedures

·         Triggers

·         Security data

·         Backup/ recovery data

Microsoft Access

 Microsoft Access is a low-end product intended for individual users and small work groups.

·        Microsoft Access tries to hide much of the underlying database technology from the user.

·        A good strategy for beginners, but not for database professionals.

What Is Microsoft Access?

·         Microsoft Access is a DBMS plus an application generator:

  -DBMS creates, processes, and administers Microsoft Access Database.

  -the application generator includes query, form, and report components.

·         The Microsoft Access DBMS engine is called Jet, which is not sold as a separate product.

 Microsoft Access 2000 and later can be used as an application generator for the Microsoft SQL  Server DBMS

Prominent DBMS Products

·         Microsoft Access 2010

·         Microsoft SQL Server 2008

  -New: Microsoft SQL Server 2012 Express

·         Oracle Corporation Oracle Database 12c

·         MySQL 5.6

·         IBM DB2 

Three Types of Database Design

·        From Existing Data

Analyse spreadsheets and other data tables

Extract data from other databases

Design using normalization principles

·       New System Development

Create data model from application requirements

Transform data model into database design

·       Database Redesign

Migrate databases to newer databases

Integrate two or more databases

Reverse engineer and design new databases using normalization principles and data model transformation

The Relational Database Model

·         The dominant database model is the relational database model  - all current major DBMS products      are based on it.

·         It was created by IBM engineer E.F. Codd in 1970

·         It was based on mathematics called relational algebra

Object Oriented DBMS (OODBMS)

·         Object-oriented programming started in the mid-1980s

·         Goal of OODBMS is to store object-oriented programming objects in a database without having to  transform them into relational format

·         Object-relational DBMS products, such as Oracle 8i and 9i, allow both relational and object views of  data on the same database

·         Currently, OODBMS have not been a commercial success due to high cost of relational to object-  oriented transformation

Functions of a DBMS

·         Data storage, retrieval, and update.

-fundamental function of DBMS

·         Transaction support

-A mechanism that ensures the all or nothing property of transactions enforced

·         Concurrency Control services

-ensures that updates are carried out properly when multiple users are accessing the same data.

·         Recovery services

-recovering the database in the event that it is damaged in some way.

·         Authorization services

-Mechanism to ensure that only authorised users can access the database

·         Support for data communication

-needs to be able to integrate with data comms software