Introduction to Database Management Systems
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Introduction to Database Management Systems






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Introduction to Database Management Systems Introduction to Database Management Systems Presentation Transcript

  • Introduction to Database Management Systems
  • Chapter 1: Introduction
    • Evolution of Database Management Systems
    • Overview of Database Management Systems
    • Database-System Design
  • Database Management System (DBMS)
    • Databases touch all aspects of our lives
    • DBMS:
      • Collection of interrelated data
      • Set of programs to access the data
    • Convenient and efficient processing of data
    • Database Applications
  • Evolution of Database Systems
    • Early days: database applications built on top of file systems
    • Drawbacks of using file systems to store data:
      • Data redundancy and inconsistency
      • Difficulty in accessing data
      • Atomicity of updates
      • Concurrency control
      • Security
      • Data isolation — multiple files and formats
      • Integrity problems
  • Abstraction
    • View level : application programs hide details of data types.
    • Logical level : what data are
    • type employee = record name : string; address : string; s alary : real; end ;
    • Physical level : how data are stored
  • Data Models
    • A collection of tools for describing
      • Data
      • Relationships among data items
      • Semantics of stored data
      • Database constraints
  • Data Models
    • Entity-Relationship model
    • Relational model
    • Other models:
      • Network
      • Hierarchical
      • Object-oriented
      • Semi-structured
  • Database Management Systems
    • Smaller and smaller systems
      • Past: large and expensive DBMS
      • Present: DBMS in most personal computers
    • More and more data stored
      • Past: few MB
      • Present: terabyte (10 12 bytes), petabyte (10 15 bytes)
  • Application Architectures Two-tier architecture Three-tier architecture
  • Database Users
    • Users are differentiated by the way they interact with the system
        • Database Administration : responsible for the structure or schema of the database (DDL), coordinates all activities regarding the database
        • Application programmers – interact with system through DML calls
        • Sophisticated users – form requests in a database query language
        • Naive users – invoke one of the permanent application programs that have been written previously
  • Data Definition Language (DDL)
    • Defines the database schema and constraints
    • DDL compiler  data dictionary
    • Metadata – data about data
  • Data Manipulation Language (DML)
    • Accessing and manipulating the data
      • DML – query language
    • Query Languages
      • Procedural – user specifies what data is required and how to get those data
      • Nonprocedural – user specifies what data is required without specifying how to get those data
    • SQL: nonprocedural query language
  • Transaction Management
    • T ransaction : unit of work to be executed atomically and in isolation from other transactions
    • Transaction-manager : ensures that the database remains in a consistent
      • system failures
      • transaction failures
    • Concurrency-control : interaction among the concurrent transactions to ensure consistency
  • ACID Properties
    • A tomicity: all-or-nothing of the transaction’s effect will take place
    • C onsistency: each transaction leaves the system in a consistent state
    • I solation: each transaction must appear to be executed as if no other transactions are executed at the same time
    • D urability: effect of a transaction must never be lost after the transaction is completed
  • Transaction Processing
    • Logging:
      • Log manager
      • Recovery manager
    • Concurrency control
      • Multiple transactions
      • Locking protocols
    • Deadlock resolution
  • Database System Studies
    • Design of the database
      • What to store, structure, semantics
      • Functionality requirement
      • Trade offs
      • Security
    • Database programming
      • How to express database operations, capability requirements, etc.
    • Database implementation
      • Query, transaction processing, storage, efficiency
  • Next Class: Entity Relationship Model (Cont.)
    • E-R model of real world
      • Entities (objects)
      • Attributes of entities
      • Relationships between entities
    • Widely used for database design
      • E-R model usually converted to design in the relational model