database
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The document provides an overview of databases and their advantages over traditional file systems. It discusses key database concepts like data hierarchy, entities and attributes, database models, and components. The main points are: - Databases organize related data centrally for efficient data sharing and management, avoiding data duplication found in file systems. - Key concepts include data hierarchy, database components, architecture with three logical levels, and entity-attribute modeling. - Popular database models include hierarchical, network, and relational models, with relational being most common today. - Database languages like DDL and DML manipulate and query the database, while the data dictionary documents the stored data.
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database
- 2. CONTENTS • INTRODUCTION • DATABASE CONCEPTS • DATA HIERARCHY • ENTITIES AND ATTRIBUTES • TYPES OF ATTRIBUTES • DATABASE COMPONENTS • DATABASE ARCHITECTURE • DATABASE MODELS • PLAYING WITH DATABASE • ADVANTAGES OF DATABASE
- 4. Limitations: Program-Data Dependence. No centralized control of data. Multiple file formats, duplication of information in different files. Each app. has its own private files & users has little chance to share data outside their own app. Each different data access request (a query) performed by a separate program.
- 5. Cont’d Creating the system requires a lot of effort For each new application, programmers have to design their own file formats & descriptions from scratch. Excessive Program Maintenance: 80% of information systems budget. Need to write a new program to carry out each new task. Data Redundancy (Duplication of data).
- 6. INTRODUCTION A database is an organised collection of related data : • ƒ Representing/capturing the information about a real-world , enterprise or part of an enterprise. • ƒ Collected and maintained to serve specific data management needs of the enterprise. • It can be of varying size and complexity . By data, we mean known facts that can be recorded.
- 7. Cont’d For example: University Database • Data about students, faculty, courses, research laboratories, course registration/ enrolment etc. • Purpose: To keep an accurate track of the academic activities of the university.
- 8. Morphbank It is a database of images that scientists use for international collaboration, research and education.
- 9. Mind Manager: is a comprehensive organizer for PC users who want to keep track of just about anything in their daily lives.
- 10. Advantages of database over file system Efficiency: highly efficient as data is stored in one central location. Minimal Data Redundancy: reduce file duplication. Data Consistency: less redundancy leads to consistency. Data Integration: Since related data is stored in one single database, enforcing data integrity is much easier.. Data Sharing: Related data can be shared across programs since the data is stored in a centralized manner.
- 11. Cont’d Better Controls: Better controls can be achieved due to the centralized nature of the system Application Development Ease: no need to write different programmes for different applications. Reduced Maintenance: Maintenance is less and easy, again, due to the centralized nature of the system. Providing backup and recovery services.
- 12. Database vs. File Systems
- 14. DATA HIERARCHY BITS 0’s and 1’s CHARACTER Combination of 0’s and 1’s 011000111(A-Z)(0-9)(!-*) FIELD Combination of characters. Name, roll no, class, rank RECORD Record of MBA 1st sem. FILE Record of each student of MBA 1st sem. DATABASE Record of MBA 1st and 4th sem.
- 16. DATABASE CONCEPTS Database management system (dbms):Software to manipulate database. Metadata : Data that describe the properties or characteristics of end-user data . Database administrator : Persons who are responsible for the overall management of data resources Database system: Comprised of database, DBMS, and application programs
- 17. Cont’d System developers: Programmers who design new application programs. End users : Who request or receive information from it. Computer-aided software engineering (case) tools: CASE tools are automated tools used to design databases and application programs.
- 18. Database management system (DBMS) • A database management system (DBMS) is a general purpose software system that: • Defines, creates, and maintains a database. • Allow access to data in database.
- 19. 3- LEVEL DATABASE SYSTEM ARCHITECTURE
- 20. Levels of database The Internal level : It is the physical level which shows how the data is stored, how bytes are transferred to and from storage devices. It interacts directly with hardware. The Conceptual level: It is the representation of the entire information content of the database. Main functions of DBMS are also defined on this level. The External Level : Represents the collection of views available to different end-users. It changes data coming from conceptual level to a format and view that is familiar to users.
- 22. TYPES OF ATTRIBUTES ATOMIC COMPOSITE SINGLE-VALUED MULTI-VALUED • DOESN’T CONTAIN MEANINGFUL SMALLER COMPONENTS- GENDER • IF IT CONTAINS ONE OR MORE COMPONENTSADDRESS- HOUSE NO. STREET NO. PIN CODE • HAVING SINGLE VALUE • AGE, NAME • MORE THAN ONE VALUE • PHONE NUMBER, ID’s DERIVED • THAT CAN BE DERIVED FROM OTHER • AGE STORED • THAT CAN BE FOUND WITH HELP OF OTHER ATTRIBUTES - DATE OF BIRTH NULL-VALUED • THAT HAVE VALUE ONLY FOR PARTICULAR ATTRIBUTE- DEGREE
- 23. Types of database models Hierarchical model Network model Relational model
- 24. Hierarchical database model Logically represented by an upside down tree Each entity have one parent but can have several parents. At top of hierarchy there is only one entity called root.
- 25. Network data model Each record can have multiple parents. Each entity can be accessed through several paths.
- 26. Relational database model RDBMS: the relational database management system (RDBMS) Relation: a relation is a 2D table has the following features: Attributes Entity Tuples
- 27. Relational database model All data is maintained in the form of tables consisting of rows and columns. Operators are provided. This, in fact, is a major reason for the relational model to become more programmer friendly and much more dominant and popular. Oracle, Sybase, DB2, Ingres, Informix, MS-SQL Server are few of the popular Relational DBMSs.
- 28. Relation A table Tuple A row or a record in a relation. Attribute A field or a column in a relation. Cardinality of a relation The number of tuples in a relation. Degree of a relation The number of attributes in a relation. Foreign Key An attribute or a combination of attributes in one relation R1 connecting it to R2 Primary Key of a relation An attribute or a combination of attributes that uniquely defines each tuple in a relation.
- 29. Degree Attributes Agent code Primary key Agent name Agent area code Agent phone 501 Alex 713 56789 502 John 615 67542 Agent code 501 Foreign key Customer code 601 Customer name Bob product 502 602 Alice Detergent Soap T U P L E C A D I N A L I T Y
- 30. Advantages Conceptual simplicity Handles more relationship types Data access flexibility Promotes database integrity Data independence Conformance to standards Disadvantages System complexity Lack of structural independence
- 32. DATA DEFINITION LANGUAGE (DDL) Collection of instructions and commands used to define and describe data and data relationships. DATA DICTIONARY Detailed description of all data used in the database. Provide a standard definition of terms and data elements DATA MANIPULATION LANGUAGE (DML) Allows users to access, modify, and make queries about data contained in the database Generate reports REPORT: A view of just a portion of a database records and/or fields as desired by user.