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Chapter 1 - Introduction to Database Systems.ppt
- 1. 7/2/2024 1 Fundamentals of Database System Dilla University College of Engineering and Technology Department of Computer Science
- 2. Introduction 7/2/2024 2 Data: What is data? Facts concerning people, objects, events or other entities. Can be in the form of text, graphics, sound and video segments They are difficult to interpret or make decisions based on Unprocessed, raw facts and can be stored in database Information: What is Information? Data presented in a form suitable for interpretation. Data processed to be useful in decision making. Processed data Can’t be stored in database
- 3. Introduction … cont’d 7/2/2024 3 Database: What is database? An organized collection of logically related data. A shared collection of logically interrelated data designed to meet the varied information needs of an organization. A shared collection – can be used simultaneously by many department and user Logically related - comprise the important objects and the relationships between these objects A computerized means of record keeping system
- 4. Introduction …. cont’d 7/2/2024 4 A database has the following implicit properties: A database represents some aspect of the real world, sometimes called the mini world or the Universe of Discourse (UoD). Changes to the mini world are reflected in the database. A database is a logically coherent collection of data with some inherent meaning. A random assortment of data cannot correctly be referred to as a database. A database is designed, built, and populated with data for a specific purpose.
- 5. Introduction …. cont’d 7/2/2024 5 Course Section Semester Name Rank MIS 3353 100 Su 01 Kemp Instr MIS 3353 200 Su 01 Schwarzkopf Assoc P MIS 3373 200 Su 01 Kemp Instr MIS 4663 900 Fa 01 Schwarzkopf Assoc P MIS 4663 901 Fa 01 Van Horn Prof Data
- 6. Introduction … cont’d 7/2/2024 6 Meta Data: What do we mean by meta data? Descriptions of the properties or characteristics of the data, including data types, field sizes, allowable values, and documentation Data that describes data Data about data Description of fields Display and format instructions Structure of files and tables Security and access rules Triggers and operational rules
- 7. Introduction …. cont’d 7/2/2024 7 Metadata Data Item Value Name Type Length Min Max Description Course Char 7 Three digit depart- ment reference and 4 digit Section Integer 3 001 900 Section number Semester Char 10 Semester and year Name Char 30 Instructor name Rank Char 10 Instructor rank
- 8. Data management approaches 7/2/2024 8 Data management : keeping your data records We have three approaches Manual Approach File-Based Approach Database Approach Manual File Handling Systems The primitive and traditional way of information handling This may work well if the number of items to be stored is small. Includes intensive human labor Events and objects are written on files (paper) Each of the files containing various kinds of information is labeled and stored in one or more cabinets The cabinets could be kept in safe places for security
- 9. Manual File Handling Systems ..cont’d 7/2/2024 9 Limitations of Manual File Handling Problem of Data Organization Problem of Efficiency Prone to error Difficult to update, retrieve, integrate You have the data but it is difficult to compile the information Significant amount of duplication of data Cross referencing is difficult Two computerized approaches evolved to overcome the limitations of the above approaches File based approach decentralised Database approach centralised
- 10. 7/2/2024 10 File based systems were an early attempt to computerize the manual filing system. It is a decentralized computerized data handling method i.e. to develop a program or a number of programs for each different application. Since every application defines and manages its own data, the system is subjected to serious data duplication problem. File based Approach
- 11. Limitations of File-Based systems 7/2/2024 11 Data Redundancy (Duplication of data) Same data is held by different programs Staffsalary(staffno, name, sex, salary) Staff(staffno,name,position,sex,dateofb,salary) Wasted space (Uncontrolled duplication of data) 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. Limited data sharing- No centralized control of data Data Inconsistency and confusion Data dependence File structure is defined in the program code and is dependent on the application programming language.
- 12. Limitations of File-Based systems .. Cont’d Incompatible file formats - Lack of data sharing and availability) Programs are written in different languages, and so cannot easily access each others files. E.g. Personnel write in C, Payroll writes in COBOL Poor Security and administration Update Anomalies Modification Anomalies Deletion Anomalies Insertion Anomalies 7/2/2024 12
- 13. Database Approach 7/2/2024 13 Here, a single repository of data is maintained. What emerged were the database and database management systems Basic Database terminologies Enterprise: an organization like library, bank, university, etc. Entity: Person, place, thing, or event about which we wish to keep data Attribute (Field): Property of an entity. E.g. Name, age, telephone, grade, sex, etc. Record: A logically connected set of one or more Attributes that describe a person, place or thing. (Logically related data) File: A collection of related records. E.g. Student file Relationship: an association among entities (entity records) Query: question asked for database
- 14. Benefits of Database systems 7/2/2024 14 Data can be shared: two or more users can access and use. Improved data accessibility: By using structured query languages, the users can easily access data without programming experience. Redundancy can be reduced: Isolated data is integrated in database. Quality data can be maintained: the different integrity constraints in the database approach will maintain the quality leading to better decision making. Inconsistency can be avoided: controlled data redundancy will avoid inconsistency of the data in the database to some extent. Transaction support can be provided: basic demands of any transaction support systems are implanted in a full scale DBMS.
- 15. Benefits of Database systems … cont’d 7/2/2024 15 Integrity can be maintained: Data at different applications will be integrated together with additional constraints. Security measures can be enforced: The shared data can be secured by data security mechanisms. Improved decision support: the database will provide information useful for decision making Standards can be enforced: ways of using different data by users Less Labor: data maintenance will not demand much resource Centralized information control: Since relevant data in the organization will be stored at one repository, it can be controlled and managed at the central level. Data Independence - Applications insulated from how data is structured and stored
- 16. Limitations and risk of database approach 7/2/2024 16 Introduction of new professional and specialized personnel High cost to be incurred to develop and maintain the system Complex backup and recovery services from the users perspective High impact on the system when failure occurs to the central system
- 17. Users and Actors of Database System 7/2/2024 17 Actors on the scene: The people whose jobs involve the day-to-day use of a large database Workers behind the scene: Those who work to maintain the database system environment, but who are not actively interested in the database itself. Actors on the Scene Database Administrators Database Designers End Users System Analysts and Application Programmers (Software Engineers)
- 18. Database Administrators 7/2/2024 18 In a database environment, the primary resource is the database itself and the secondary resource is the DBMS and related software. Administering these resources is the responsibility of the Database Administrator (DBA). The DBA is responsible for authorizing access to the database, for coordinating and monitoring its use, and for acquiring software and hardware resources as needed. The DBA is accountable for problems such as breach of security or poor system response time.
- 19. Database Designer 7/2/2024 19 Database designers are responsible for identifying the data to be stored in the database and for choosing appropriate structures to represent and store this data. It is the responsibility of database designers to communicate with all prospective database users, in order to understand their requirements, and to come up with a design that meets these requirements. In many cases, the designers are on the staff of the DBA and may be assigned other staff responsibilities after the database design is completed. The final database design must be capable of supporting the requirements of all user groups.
- 20. End Users 7/2/2024 20 End users are the people whose jobs require access to the database for querying, updating, and generating reports; The database primarily exists for their use. There are several categories of end users: Casual end users:- occasionally access the database. They are typically middle or high-level managers or other occasional browsers. Naive or parametric end users:- Their main job revolves around constantly querying and updating the database, using standard types of queries and updates called canned transactions that have been carefully programmed and tested. Bank tellers check account balances and post withdrawals and deposits Reservation clerks for airlines, hotels, and car rental companies check availability for a given request and make reservations
- 21. End Users … Cont’d 7/2/2024 21 Sophisticated end users: Include engineers, scientists, business analysts, and others who thoroughly familiarize themselves with the facilities of the DBMS so as to implement their applications to meet their complex requirements. Stand-alone users: Maintain personal databases by using ready made program packages that provide easy to use menu or graphics based interfaces. An example is the user of a tax package that stores a variety of personal financial data for tax purposes.
- 22. System Analysts and Application Programmers (Software Engineers) 7/2/2024 22 System analysts: Determine the requirements of end users, especially naive and parametric end users, and develop specifications for canned transactions that meet these requirements. Application programmers implement these specifications as programs; then they test, debug, document, and maintain these canned transactions. Such analysts and programmers (nowadays called software engineers) should be familiar with the full range of capabilities provided by the DBMS to accomplish their tasks.
- 23. Workers behind the Scene 7/2/2024 23 These persons are typically not interested in the database itself. These include: DBMS system designers and implementers:-are persons who design and implement the DBMS modules and interfaces as a software package. A DBMS is a complex software system that consists of many components or modules, including modules for implementing the catalog, query language, interface processors, data access, concurrency control, recovery, and security. The DBMS must interface with other system software, such as the operating system and compilers for various programming languages
- 24. Workers behind the Scene … cont’d 7/2/2024 24 Tool developers: Include persons who design and implement tools Tools are software packages that facilitate database system design and use, and help improve performance. Tools are optional packages that are often purchased separately. They include packages for database design, performance monitoring, natural language or graphical interfaces, prototyping, simulation, and test data generation. Operators and maintenance personnel: are the system administration personnel who are responsible for the actual running and maintenance of the hardware and software environment for the database system.
- 25. Some Common uses of Databases 7/2/2024 25 In a university Containing information about a student, the course she/he is enrolled in, the dormitory she/he has been given. Containing details of Staff who work at the university at personnel, payroll, etc. In a library There may be a database containing details of the books in the library and details of the users, The database system handles activities such as Allowing a user to reserve a book Notifying when materials are overdue:
- 26. Some Common uses of Databases … Cont’d 7/2/2024 26 In travel agencies When you make inquiries about a travel, the travel agent may access databases containing flight details Flight no., date, time of departure, time of arrival Insurance When you wish to take out insurance, there is database containing Your personal details: name, address, age information on whether you drink or smoke, Your medical records to determine the cost of the insurance Supermarkets When you buy goods from some supermarkets, a database will be accessed. The checkout assistant will run a barcode reader over the purchases.
- 27. 7/2/2024 27