chapter 1 Introduction to Database Systems Best.pdf
0 likes43 views
Chapter 1 introduces database systems, covering basic definitions, drawbacks of file systems, and the advantages of using databases over traditional methods. It discusses the roles of various users, typical DBMS functionalities, data models, and database languages, emphasizing the importance of structured data management. The chapter concludes by highlighting scenarios when using a database may not be necessary due to costs or specific operational needs.
chapter 1 Introduction to Database Systems Best.pdf
- 1. CHAPTER 1:INTRODUCTION TO Database Systems Basic Definitions Drawbacks of file systems Database Applications Roles in Database Design & Database Users Typical DBMS Functionality Data models Database Languages (DDL, DML,DCL) Main Characteristics of the Database Approach Advantages of Using the Database Approach When Not to Use Databases 1
- 2. 1.1 BASIC DEFINITIONS 2 Data: Known facts that can be recorded and have an implicit meaning. be thought of as a description of the World. names, telephone(text,number,image etc) numbers, and addresses of the people you know. Data may represent bit,field,record…. Information expand our knowledge beyond the range of our senses. e.g. If I take a picture of you, the photograph is information. But what you look like is data. When data is processed, organized, structured or presented in a given context so as to make it useful, it is called information
- 3. CONT… 3 file Is an object on a computer that stores data, information, settings, or commands that are used with a computer program. group of related records. A. Each student's test score? B.The average score of a class or of the entire school?
- 4. File based system Collection of application programs that perform services for the end users wishing to information. Database: A collection of related data. data recorded in an indexed address book, or you may have stored it on a hard drive, using a personal computer and soft ware such as MicrosoftAccess,Excel or SQL software. simply an organized collection of related data, typically stored on disk, and accessible by possibly many concurrent users. Databases are generally separated into application areas. For example, one database may contain Human Resource (employee and payroll) data; another may contain sales data; another may contain accounting data; and so on. Databases are managed by a DBMS. 4
- 5. CONT.. DATABASE MANAGEMENT SYSTEM (DBMS): A software package/ system to facilitate the creation and maintenance of a computerized database. provides users and programmers with a systematic way to create, retrieve, update and manage data. DATABASE SYSTEM: The DBMS software together with the data itself. Sometimes, the applications are also included. 5
- 7. CONT… Data Redundancy (Duplication of data):- Different systems/programs have separate copies of the same data Multiple file formats, duplication of information in different files Requires space, effort and result in loss of data & metadata integrity Limited Data Sharing :-No centralized control of data Each application has its own private files & users has little chance to share data outside their own applications 7
- 8. CONT…. Lengthy Development Times:- For each new application programmers must design their own file formats & descriptions from scratch Excessive Program Maintenance:- 80% of information systems budget Difficulty in accessing data Need to write a new program to carry out each new task Integrity problems Integrity constraints Hard to add new constraints or change existing ones 8
- 9. 9 What is the solution?
- 10. THE SOLUTION Unique and centralized administration of data in a given company i.e. database notion What is a Database? A database is a collection of related data It represents some aspects of the real world.(miniworld) It is a logically coherent collection of data with some inherent meaning. It is designed for specific purpose and intended users. It can be at varying size and complexity It can be generated and maintained manually 10
- 11. 1.3 DATABASE DEFINITIONS A database represents some aspect of the real world, sometimes called the Mini world or the universe of discourse (UoD). Changes to the miniworld 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 . It has an intended group of users and some preconceived applications in which these users are interested. In other words, a database has some source from which data is derived, some degree of interaction with events in the real world, and an audience that is actively inter- ested in its contents. 11
- 12. 1.3 DATABASE APPLICATIONS Traditional Applications: if we go to the bank to depositor withdraw funds, if we make a hotel or airline reservation, if we access computerized library catalog to search for a bibliographic item, or if we buy some item-such as a book, toy, information are stored by Numeric and Textual Databases. More Recent Applications: Multimedia Databases Geographic Information Systems (GIS) Data Warehouses Real-time and Active Databases Many other applications 12
- 13. 1.4 ROLES IN DATABASE DESIGN & DATABASE USERS Database Administrator (DBA) Database Designers Application Programmers End Users (naive and sophisticated) Users may be divided into Those who actually use and control the database content, and those who design, develop and maintain database applications (called “Actors on the Scene”), and Those who design and develop the DBMS software and related tools, and the computer systems operators (called “Workers Behind the Scene”). 13
- 14. CONT…. Actors on the scene Database administrators: Responsible for authorizing access to the database, for coordinating and monitoring its use, acquiring software and hardware resources, controlling its use and monitoring efficiency of operations. Database Designers: Responsible to define the content, the structure, the constraints, and functions or transactions against the database. They must communicate with the end-users and understand their needs. 14
- 15. CONT… Actors on the scene (continued) End-users: They use the data for queries, reports and some of them update the database content. End-users can be categorized into: Casual: access database occasionally(irregular infrequent) when needed Naïve or Parametric: they make up a large section of the end-user population. They use previously well-defined functions in the form of “canned/preserved transactions” against the database. Examples are bank-tellers or reservation clerks who do this activity for an entire shift of operations. 15
- 16. CONT….. 16 Sophisticated: • These include business analysts, scientists, engineers, others thoroughly familiar with the system capabilities. • Many use tools in the form of software packages that work closely with the stored database. Stand-alone: • Mostly maintain personal databases using ready-to-use packaged applications. • An example is a tax program user that creates its own internal database. • Another example is a user that maintains an address book
- 17. 1.5TYPICAL DBMS FUNCTIONALITY 1.5 TYPICAL DBMS FUNCTIONALITY 17
- 18. CONT…. Defining a particular database in terms of its data types, structures/relation/, and constraints/limitation or restriction/ Constructing or Loading the initial database contents on a secondary storage medium Manipulating the database: Retrieval: Querying, generating reports Modification: Insertions, deletions and updates to its content Accessing the database through Web applications Processing and Sharing by a set of concurrent users and application programs – yet, keeping all data valid and consistent 18
- 19. CONT….. Other features: Protection or Security measures to prevent unauthorized access “Active” processing to take internal actions on data Presentation and Visualization of data Maintaining the database and associated programs over the lifetime of the database application Called database, software, and system maintenance 19
- 20. COMPONENTS OF DBMS ENVIRONMENT HARDWARE Can range from a PC to a network of computers. SOFTWARE DBMS, operating system, network software (if necessary) and also the application programs. DATA Used by the organization and a description of this data called the schema. PROCEDURES Instructions and rules that should be applied to the design and use of the database and DBMS. PEOPLE 20
- 21. DATA MODELS A set of concepts to describe the structure of a database, the operations for manipulating (control) these structures, and certain constraints that the database should obey. Data Model Structure and Constraints: Constructs are used to define the database structure/relation Constructs typically include elements (and their data types) as well as groups of elements (e.g. entity, record, table), and relationships among such groups Constraints specify some restrictions on valid data; these constraints must be enforced at all times. 21
- 22. CONT…. Operations on the data model to built it may include basic model operations (e.g. generic insert, delete, update) and user-defined operations (e.g. compute_student_gpa, update_inventory) 22
- 23. CATEGORIES OF DATA MODEL 23 Conceptual (high-level, semantic) data models: Provide concepts that are close to the way many users perceive/aware or conscious/ data. • (Also called entity-based or object-based data models.) Physical (low-level, internal) data models: Provide concepts that describe details of how data is stored in the computer.These are usually specified in an ad-hoc/spesfic purpose/ manner through DBMS design and administration manuals Implementation (representational) data models: Provide concepts that fall between the above two, used by many commercial DBMS implementations (e.g. relational data models used in many commercial systems).good for end user.
- 24. 24 1.7 DATABASE LANGUAGE(DDL, DML,DCL) DATA-DEFINITION LANGUAGE(DDL):We specify a database schema by a set of definition expressed by a special language called a Data-Definition Language. For instance, the following statement in the SQL language defines the account table: e.g. create table account(account- number char (10),balance integer) Execution of the above DDL statement create the account table. In addition, it updates a special set of tables called the DATA DICTIONARY or DATA DIRECTORY
- 25. 25 The retrieval of information stored in the database. The insertion of new information into the database. The deletion of information from the database. The modification of information stored in the database. A data-manipulation language(DML) is a language that enables users to access or manipulate data as organized by the appropriate data model. Eg The query in the SQL language finds the name of the customer whose customer-id is 1999: e.g. Select customer.customer-name from customer where customer.customer-id=1999 DATA-MANIPULATION LANGUAGE:
- 26. 1.8 MAIN CHARACTERISTICS OFTHE DATABASE APPROACH Self-Describing Nature of a Database System is that the database system contains not only the database itself but also complete definition or description of the database structure and constraints. This definition is stored in the DBMS catalog, which contains information such as the structure of each file, the type and storage format of each data item, and various constraints on the data. The information stored in the catalog is called meta-data, and it describes the structure of the primary database 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. 26
- 27. CONT…… Sharing of data and multi-user transaction processing: Allowing a set of concurrent users to retrieve from and to update the database. Concurrency control within the DBMS guarantees that each transaction is correctly executed or aborted. Recovery subsystem ensures each completed transaction has its effect permanently recorded in the database OLTP (Online Transaction Processing) is a major part of database applications. This allows hundreds of concurrent transactions to execute per second. 27
- 28. 1.9 ADVANTAGES OF USING THE DATABASE APPROACH Controlling redundancy in data storage and in development and maintenance efforts. Sharing of data among multiple users. Restricting unauthorized access to data. Providing constant storage for program Objects Providing Storage Structures (e.g. indexes) for efficient Query Processing Providing backup and recovery services. Providing multiple interfaces to different classes of users. Representing complex relationships among data. Enforcing integrity constraints on the database. 28
- 29. 29 CONT…. Reduced application development time: Incremental time to add each new application is reduced. Flexibility to change data structures: Database structure may evolve as new requirements are defined. Availability of current information: Extremely important for on-line transaction systems such as airline, hotel, car reservations.
- 30. CONT… Economies of scale: Wasteful overlap of resources and personnel can be avoided by combining data and applications across departments. 30
- 31. 31 WHEN NOT TO USE DATABASE Main inhibitors (costs) of using a DBMS: High initial investment and possible need for additional hardware. Overhead for providing generality, security, concurrency control, recovery, and integrity functions. When a DBMS may be unnecessary: If the database and applications are simple, well defined, and not expected to change. If there are inflexible real-time requirements that may not be met because of DBMS overhead. If access to data by multiple users is not required.
- 32. CON’T… When no DBMS may be sufficient: If the database system is not able to handle the complexity of data because of modeling limitations If the database users need special operations not supported by the DBMS. 32
- 33. READING ASSIGMENT ONE What are ANSI-SPARC Architecture ? Define them ? 33