سارة

• DBMS


  A set of system software that facilitates the management and control of the database
• DBMS

  A collection of inter-related data and set of programs to store & access those data in an easy and effective manner
• Purpose of database systems

  • Manage the data (e.g. students, teachers, courses, books)
• DBMS


  • Allows storing data in a way that enables adding new data, deleting unused data, updating outdated data, retrieving data efficiently
• DBMS


  • Considered very useful for manufacturing situations
• DBMS components

  • Data Model
  • Data Dictionary
  • Data Definition Language (DDL)
• Data Model


  A conceptual method of structuring data (e.g. hierarchical, networked, relational)
• Data Dictionary


  The "database" table of contents, defines the database and identifies the data items used
• Data Definition Language (DDL)


  Defines what types of information are in the database and how they will be structured
• Objectives and advantages of a DBMS

  • Maintain integrity of data
  • Maintain non-redundancy of data
  • Maintain security and privacy of data
  • Provide access to multiple users
  • Provide an integrated and shared system
• Disadvantages of a DBMS

  • Costly due to requirements of expensive hardware and higher operating costs
  • Greater complexity of backup and recovery in multiuser environments
  • High risk of data loss, due to centralization of the database
• DBMS Architecture Levels

  • External level
  • Conceptual level
  • Internal level
• External level


  Also called view level, where users can view their desired data without needing to know the database schema details

  
• Conceptual level


  Also called logical level, describes the whole design of the database including relationships, schema, constraints and security
• Internal level

  Also known as physical level, describes how the data is actually stored in the storage devices and allocates space to the data
• Relational model (RM)


  Can represent as a table with columns and rows. Each row is known as a tuple. Each table of the column has a name or attribute.
• Popular Relational DBMS

  • Oracle and RDB - Oracle
  • SQL Server and Access - Microsoft
• Relational Model Concepts in DBMS

  • Attribute
  • Tables
  • Tuple
  • Relation Schema
  • Degree
  • Cardinality
  • Column
  • Relation instance
  • Relation key
  • Attribute domain
• Properties of Relations

  • Name of the relation is distinct from all other relations
  • Each relation cell contains exactly one atomic (single) value
  • Each attribute contains a distinct name
  • Attribute domain has no significance
  • Tuple has no duplicate value
• Relational Integrity Constraints

  • Domain Constraints
  • Key Constraints
  • Referential Integrity Constraints
• Domain Constraints

  Attribute value must be in the corresponding domain and of the appropriate data type
• Data


  Raw facts that are collected
• Internet


  A global network of computer networks
• Computer Network

  A group of computers or devices linked to each other that enables the computer to communicate with another computer and share their resources, data, and applications
• Data refers to any information which is presented in a form that is agreed and accepted upon by its creators and users
• Devices in a computer network

  • Computers
  • Telephones
  • Other communication devices
• Key Constraints

  An attribute that can uniquely identify a tuple in a relation
• Forms of data used in communications

  • Text
  • Numbers
  • Images
  • Audio
  • Video
• Text


  • Combination of alphabets in small case as well as upper case, stored as a pattern of bits, prevalent encoding systems: ASCII, Unicode
• Internet

  • Connects computers and servers across the world using routers, switches and telephone lines, and other communication devices and channels
  • Runs on Transmission Control Protocol/Internet Protocol (TCP/IP protocol) which deals with communication and helps to establish the connection between two computers and ensures that data sent from one end is delivered intact at the other intended destination

  
• Numbers


  • Combination of digits from 0 to 9, stored as a pattern of bits, prevalent encoding systems: ASCII, Unicode
• Computer network


  • Connection between two or more autonomous computers for information interchange

  
• Referential Integrity Constraints


  Based on the concept of Foreign Keys. A foreign key is an attribute of a relation which should be referred to in other relationships.
• World Wide Web (WWW)

  A network of computers and servers (client/server architecture) created by connecting them through the Internet<|>The internet is the backbone of the web as it provides the technical infrastructure to establish the WWW and acts as a medium to transmit information from one computer to another computer<|>Uses web browsers to display the information on the client, which it fetches from web servers

  
• Media for connecting computers

  • Copper wires
  • Microwaves
  • Optical fibers
  • Satellite
• Images


  • Digitally stored, a pixel is the smallest element, size depends on number of pixels and bit pattern used to indicate pixel value, common formats: jpg, png, bmp
• Types of keys

  • Primary key
  • Candidate key
  • Foreign key

  
• Functions of the web

  • As a part of the operating system Windows/Unix
  • As a distribution channel for downloading applications on the operating platform
  • As a middleware between database servers and clients
• Types of networking

  • Local Area Network (LAN)
  • Wide Area Network (WAN)
  • Metropolitan Area Network (MAN)

  
• Audio


  • Data in the form of sound, continuous not discrete, can be recorded and broadcasted