INTRODUCTION TO DATABASES

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INTRODUCTION TO DATABASES Chapter 1 INTRODUCTION TO DATABASES Pearson Education © 2014

Chapter 1 - Objectives Some common uses of database systems. Characteristics of file-based systems. Problems with file-based approach. The meaning of the term ‘database’. Meaning of the term Database Management System (DBMS). Major components of the DBMS environment. Users involved in the DBMS environment. Advantages and disadvantages of DBMSs. Pearson Education © 2014

Database Concepts Data: numbers, strings, text, date, time, timestamp, is a meaningless static value. Known facts that can be recorded and have an implicit meaning. ex)What does 3421 means? facts about entities Person's name, Phone, address, email, picture, … Student's ID, name, subjects taken, results,… Product's name, description, manufacturer, price,… Book's publisher, author, title,… facts about relationships BADER lives in Riyadh Nora bought a book from university books shop on 01/03/11 Notice the different types of data numbers, strings, text, date, time, timestamp, Text, picture, audio, video, graphics …

Database Concepts Information: is the data you process in a manner that makes it meaningful. Information can be provided only if proper data exists. Data VS information Data itself has no meaning without meta data which describes data For example : 1012674, 28761, 153 Data does not give us any information, but knowing the meta data that explains data : Staff_ID, Phone Number, room number Information : is the data you process in a manner that makes it meaningful. Data is what you store in database. Information is what you retrieve from a database.

Database Concepts Database (DB): Two examples is a collection of related persistent data. Can be generated & maintained manually or automatically A collection of logically related data, including metadata ”data about data”, that describes data Data: name , city, birth Metadata: name - string, length<10 Khaled, Dammam ,01/01/70 city – string, length<15 Sara , Abha , 01/03/01 birth – date, format DD/MM/YY Two examples all data required for the management of student records in a university. all data required for the management of books and borrowers in a library.

Database Concepts Database Management System (DBMS) a software system that enables users to create, maintain, and query the database Most DBMSs now have facilities that make data access fast, reliable, secure and easy Example DBMSs Oracle MS Access MySQL

Database Concepts Database application: a program that interacts with the database at some point in it’s execution . built on top of DBMS to satisfy end users special requirements and preference A database application is usually implemented using a Database Management System (DBMS). Database System (DBS) is (DB + Software (DBMS + Application program)).

(DB +Software (DBMS + Application program) ) Database Concepts Database System Database System: is a collection of data and the programs interacts with the database. OR the DBMS software together with the data itself. Sometimes, the applications are also included. (DB +Software (DBMS + Application program) ) To manage large amounts of data Efficiently Reliably Securely conveniently

Database Environment DBS Application Programs DBMS Query Process Data Access Meta-Data Database

Types of Databases Numeric and Textual Databases Multimedia Databases Geographic Information Systems (GIS) Data Warehouses Real-time and Active Databases Lecture1

Examples of Database Applications Purchases from the supermarket Purchases using your credit card Booking a holiday at the travel agents Using the local library Studying at university Pearson Education © 2014

File-Based Systems Collection of application programs that perform services for the end users (e.g. reports). Each program defines and manages its own data. File handling Data Entry User 1 File Definition Application Program 1 File1 File handling Data Entry User 2 File Definition Application Program 2 File 2 Pearson Education © 2014

Limitations of File-Based Approach Separation and isolation of data Each program maintains its own set of data. Users of one program may be unaware of potentially useful data held by other programs. Duplication of data Same data is held by different programs. Duplication wasteful, it cost time and money. Wasted space and potentially different values and/or different formats for the same item. It can lead to loss of data integrity, the data will not be consistent. Pearson Education © 2014

Limitations of File-Based Approach Data dependence (program_data dependence) File structure is defined in the program code. The changes to an existing structure are difficult to make. Incompatible file formats Programs are written in different languages, and so cannot easily access each other’s files. This can be time consuming and expensive. Fixed Queries/Proliferation of application programs Programs are written to satisfy particular functions. Any new requirement needs a new program. 214 MIS

Database Approach Arose because: Definition of data was embedded in application programs, rather than being stored separately and independently. No control over access and manipulation of data beyond that imposed by application programs. Result: the database and Database Management System (DBMS). Pearson Education © 2014

Database Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. The description of the data is known as the system catalog, ( data dictionary or meta_data- the data about data) Pearson Education © 2014

Database Approach Lecture1

Database Management System (DBMS) A software system that enables users to define, create, maintain, and control access to the database. (Database) application program: a computer program that interacts with database by issuing an appropriate request (SQL statement) to the DBMS. Pearson Education © 2014

Database Management System (DBMS) Major Relational DBMS vendors/products: Oracle MS Access MySQL DB2 by IBM

Main Characteristics of the Database Approach Self-describing nature of a database system: A DBMS catalog stores the description of the database. The description is called (meta-data). This allows the DBMS software to work with different databases. Insulation between programs and data: Called program- data independence. Allows changing data storage structures and operations without having to change the DBMS access programs (application program). Lecture1

Main Characteristics of the Database Approach Abstraction is the process of recognizing and focusing on important characteristics of a situation or object and leaving/filtering out the un-wanted characteristics of that situation or object Main Characteristics of the Database Approach Data Abstraction: A data model is used to hide storage details and present the users with a conceptual view (external definition ) of the database. We can change the internal definition of an object without affecting the user of the object. Support of multiple views of the data: Each user may see a different view of the database, which describes only the data of interest to that user. Lecture1

Views Allows each user to have his or her own view of the database. A view is essentially some subset of the database. Benefits: Reduce complexity by letting users see the data in the way they want to see it. Provide a level of security Views provide a mechanism to customize the appearance of the database, Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed Pearson Education © 2009

Views view1 view2 Salary Age LName FName Staff_No LName FName Salary Bno LName FName Bno Salary DOB Age LName FName Staff_No Pearson Education © 2009

Main Characteristics of the Database Approach Sharing of data and multiuser transaction processing : allowing a set of concurrent users to retrieve and to update the database. Concurrency control within the DBMS guarantees that each transaction is correctly executed or completely aborted. OLTP (Online Transaction Processing) is a major part of database applications. Lecture1

the database management system (dbms) A software system that enables users to define ,create, maintain and control access to the database. Facilities: It allow users to define the database usually through a Data Definition Language (DDL) It allow users to access the data usually through a Data Manipulation Language (DML) It provides controlled access to the database : security system, an integrity system, concurrency system, recovery control, and a user accessible catalog

Database Approach Data definition language (DDL): DDL is a descriptive language for defining the database schema. Permits specification of data types, structures and any data constraints. All specifications are stored in the database. Pearson Education © 2014

Database Approach Data manipulation language (DML): DML is a language for retrieving and updating (insert, delete, and modify) the data in the DB. General enquiry facility (query language) of the data.

Components of DBMS Environment Pearson Education © 2014

Components of DBMS Environment Hardware Can range from a PC to a single mainframe ,to a network of computers. Depends on the organization’s requirements and the DBMS used. Software DBMS, operating system, network software (if necessary) and also the application programs. Data Used by the organization the database contains operational data and the meta data. The structure of the database is called the schema. Pearson Education © 2014

Components of DBMS Environment Procedures Instructions and rules that should be applied to the design and use of the database and DBMS. The users of the database require documented procedures on how to use or run the system. People Pearson Education © 2014

Roles in the Database Environment Data administration (DA) Database Administrator (DBA) Database Designers (Logical and Physical) System Analysis Application Programmers Database Users (naive and sophisticated) Pearson Education © 2014

Roles in the Database Environment Communicate Procedure User Requirement Write Write DB Designer System Analyst Application programmer Design Program Manage DBA App Program DBMS Use Naïve End User DB Use Sophisticated End User H/W

Database Users System Analyst: Determine the user requirements and develop the system specifications. Database Designers: In a large database :Logical database designer and physical database designer Logical database designer :responsible for defining the content, the structure, the constraints, and functions or transactions in the database. Physical database designer decides how the logical database design is to be physically realized. Application Programmer Implement programs meet the end user needs Test , debug , document, and maintain transactions Lecture1

Database Users Data administrators: responsible for: Management of data resource including database planning, development and maintenance. Policies and procedures. And conceptual /logical database design Lecture1

Database Users Database administrators: responsible for: Physical realization of the database including physical database design and implementation. authorizing access to the database coordinating and monitoring the DB use acquiring software, and hardware resources monitoring efficiency of operations. Lecture1

Database Users End-users: they use the data for queries, reports and some of them actually update the database content. Categories of End-users: Naïve : (Queries / modifies data) they unaware of DBMS They make up a large section of the end-user population. They use previously well-defined functions ,entering simple commands or choosing options from a menu. Examples: bank-tellers or reservation clerks. Sophisticated : Forms requests in a database query language. Lecture1

Advantages of DBMS Control of data redundancy Data consistency More information from the same amount of data Sharing of data Improved data integrity Improved security Pearson Education © 2014

Disadvantages of DBMS Complexity Size Cost (DBMS, Hardware, Staff, Training) Performance Higher impact of a failure Pearson Education © 2014