1 Lecture1 Introduction to Databases Systems Database 1

Book DATABASE SYSTEMS A practical Approach To Design, Implementation and Manipulation Fifth Edition Thomas Connolly Carolyn Begg 2

Course Objectives  Introduction to very basics  Guides through different design stages  Familiarize with tools  Emphasis on design stages of database 3

Course Objectives 4  Typical functions of a DBMS.  Ability to design, develop and implement a relational database for an application.  Understanding of relational Model.  Major components of the DBMS environment.  Personnel involved in the DBMS environment.  A basic understanding of SQL Language.

Lecture Objectives  Some common uses of database systems.  Characteristics of file-based systems.  Problems with file-based approach.  Meaning of the term database.  Meaning of the term Database Management System (DBMS).

Examples of Database Applications  Purchases from the supermarket  Purchases using your credit card  Booking a holiday at the travel agents  Using the local library  Renting a video  Using the Internet  Studying at university

Data, Information, Database and DBMS Data are facts. E.G Fatemh Al-Malic. Data are processed to create Information E.G Fatemh Al-Malic Grade Name : Fatemah Al-Malic Subject/ Grade : INFT2040 A CS2213 B 7

Figure 1-1a Data in Context Context helps users understand data

Graphical displays turn data into useful information that managers can use for decision making and interpretation

Definitions of Database and DBMS  Database is collection of related data and information  Database Management System (DBMS) is a software package that is used to create, access and maintain database.

Requirement of today’s Information System Store Large amount of data. Efficient(fast )access & manipulation of data. Concurrent access by Large number of users. Security. Reliability. Data Integrity. Transaction Processing. 11

File Processing System  A collection of application programs that perform services for the end-users such as production of reports  Each program defines and manages its own data  You can create file and store data. 12

Disadvantages of File Processing  Sequential Access  Not efficient for large data amount  Duplication of Data (Data Redundancy)  Different systems/programs have separate copies of the same data Same data is held by different programs. Wasted space and potentially different values and/or different formats for the same item.  Limited Data Sharing  No centralized control of data  Programs are written in different languages, and so cannot easily access each other’s files. Cannot span disks Files can not span multiple disks.

Disadvantages of File Processing  Vulnerable to Inconsistency  Change in one table need changes in corresponding tables as well otherwise data will be inconsistent 14

Problems with Data Redundancy  Waste of space to have duplicate data  Causes more maintenance headaches  The biggest problem:  When data changes in one file, could cause inconsistencies ( Vulnerable to Inconsistency )

SOLUTION: The DATABASE Approach  Central repository of shared data  Data is managed by a controlling agent  Stored in a standardized, convenient form This requires a Database and Database Management System (DBMS)

17 Advantages of Database Approach Registration Examination Library Applications Library Examination Applications Registration Applications Database Management System University Students Database - Data Sharing- Data Independence - Controlled Redundancy- Better Data Integrity

Database Management System DBMS manages data resources like an operating system manages hardware resources

DBMS Environment There are many different types of persons in developing, maintaining and using a database in an organization. End-Users : all users for which the system was developed(customers, employees). Application Developers: Develop program that access the database. Database Designer: Designing the database. Database Administrator (DBA): Create and maintain database and system. 19

Three Level Database Architecture DBMS

DBMS Architecture The Internal or Physical Level: Describes data structure, indexes etc. that deal with the storage of the data. And it provides a low-level description of the physical database, and an interface between the operating system's file system and the record structures used in higher levels of abstraction. At this level record types and methods of storage are defined, as well as how stored fields are represented.

DBMS Architecture The Conceptual Level: It presents a logical view of the entire database, which allows you to bring all the data in the database together and see it in a consistent manner. Provides an integrated conceptual view of all the data stored in the data base.

DBMS Architecture The External or View Level: It provides a window on the conceptual view which allows the user to see only the data of interest to them. application user The user can be either an application program or an end user. The different applications views different parts of the database. The System Administrator and the DBA are special cases. Because they have responsibilities for the design and maintenance for the design and maintenance of the database, they at times need to be able to see the entire database. The external and the conceptual view are functionally equivalent for these two users.

Database Design Process Requirements Analysis. Facts findings techniques(interview, research..etc) Conceptual Database Design. Using Entity- Relationship Model(ER) model Logical database Design. Using Relational database schema. Physical Database Design. Storages structures and access methods are considered for efficient access. 24