database concepts

• Database


  Specialized structure that allows computer-based systems to store, manage, and retrieve data very quickly
• Databases are valuable assets for decision making
• Database design


  • Defines the database's expected use
  • Different approach needed for different types of databases
  • Avoids redundant data
  • Poorly designed database generates errors that can lead to bad decisions and failure of organization
• Database design is the process that yields the description of the database structure and determines the database components
• Managing data with file systems is obsolete
• Understanding file system characteristics makes database design easier to understand
• Awareness of problems with file systems is important
• Data


  Raw facts and figures that do not have any meaning until processed and given a context
• Information


  Data which has been processed within a context in order to give it meaning
• Information examples


  • Average test scores
  • Most popular ice cream flavour
  • Holiday cottage booking patterns

  
• Knowledge


  Familiarity, awareness, and understanding of information as it applies to an environment. New knowledge can be derived from old knowledge.
• Database Management System (DBMS)


  Collection of programs that manages database structure and controls access to data. Acts as an intermediary between the user and the database, enabling data sharing and presenting an integrated view of the data.
• Types of databases by number of users

  • Single-user database
  • Multiuser database
  • Workgroup database
  • Enterprise database
• Types of databases by location

  • Centralized database
  • Distributed database
  • Cloud database
• Types of databases by use

  • Transactional (or production) database
  • Data warehouse
• Database design


  The process that yields the description of the database structure and determines the database components
• Example of a poor design


  • It would be difficult, if not impossible, to produce an alphabetical listing of employees based on their last names
• Evolution of File System Data Processing

  1. Manual File Systems

  2. Computerized File Systems

  3. File System Redux: Modern End-User Productivity Tools
• Manual File Systems


  • Collection of file folders kept in file cabinet
  • Organization within folders based on data's expected use (ideally logically related)
  • System adequate for small amounts of data with few reporting requirements
  • Finding and using data in growing collections of file folders became time-consuming and cumbersome
• Computerized File Systems


  • Generating reports from manual file systems was slow and cumbersome
  • Data processing (DP) specialist was hired to create a computer-based system that would track data and produce required reports
  • Initially, the computer files within the file system were similar to the manual files
• Structural dependence


  Access to a file is dependent on its own structure
• Structural independence


  File structure is changed without affecting the application's ability to access the data
• Data dependence


  Changes in the data storage characteristics without affecting the application program's ability to access the data
• Logical data format


  How the human being views the data
• Physical data format


  How the computer "sees" the data
• Field definitions and naming conventions

  Flexible record definition anticipates reporting requirements by breaking up fields into their component parts
• Data redundancy


  Exists when the same data are stored unnecessarily at different places
• Types of data anomalies


  • Update anomalies
  • Insertion anomalies
  • Deletion anomalies
• File system


  Many separate and unrelated files
• Database


  Logically related data stored in a single logical data repository
• Database system


  An organization of components that define and regulate the collection, storage, management and use of data within a database environment
• Parts of the database system environment

  • Hardware
  • Software
  • People
  • Procedures
  • Data
• Types of users in a database system

  • Systems administrators
  • Database administrators (DBAs)
  • Database designers
  • Systems analysts and programmers
  • End users
• DBMS functions


  • Data dictionary management
  • Data storage management
  • Data transformation and presentation
  • Security management
  • Multiuser access control
  • Backup and recovery management
  • Data integrity management
  • Database access languages and application programming interfaces
  • Database communication interfaces
• Why use a DBMS?

  • Data independence and efficient access
  • Reduced application development time
  • Data integrity and security
  • Uniform data administration
• Shift from computation to information
• Datasets increasing in diversity and volume
• DBMS encompasses most of CS
• Data are raw facts. Information is the result of processing data to reveal its meaning
• To implement and manage a database, use a DBMS