Database technology-overview (database, database management system, database system difference)

Database technology-overview (difference between DB, DBMS, DBS)

• Database development

  • The first generation: hierarchical, mesh database-the way the upper pointer points to the next pointer
  • The second generation: relational database technology-store data in the form of two-dimensional tables
  • The third generation: a new generation of application databases-object-oriented databases, XML databases, etc.

• Mainstream database products

  • Oracle
  • DB2-used in the enterprise
  • Microsoft SQL Server
  • Sybase: the first to propose a C / S architecture
  • Open source database
  • Mysql
  • Ingress

• Basic concepts of database

  • Data

    • Definition: a symbolic record describing things
    • Storage objects in the database, including numbers, text, graphics, images, sounds, etc.

  • Database (DB)

    • Long-term storage in computers, organized and sharable large collection of data
      

  • Database Management System (DBMS)

    • A layer between the user and the operating systemData management software
    • Features:
      • Data definition function: provide data definition language DDL, translation processing program
      • Data manipulation function: provide data manipulation language DML, compiler
      • Data organization, storage, management
      • Database operation management
      • Database establishment and maintenance

  • Database System (DBS)

    • Definition: In a computer systemThe system after the introduction of the databaseConstitute
    • Composition: database, database management system, application system, database administrator
      

  • Database Application System (DBAS)

    • Supported by DBMS, it is formed by the combination of database system and various user applications

  • Database administrator

    • Determine the content and structure of database information
    • Decide on the database storage structure and storage strategy
    • Determine integrity constraints
    • Monitor the use and operation of the database
    • Improved reorganization of the database

• Data management

  • Definition: Carry on the dataClassification, organization, coding, storage, retrieval, maintenance
  • development of:
    • Manual management stage
    • File system stage
    • Database system stage

• Characteristics of database system

  • Structured overall data
  • Easy data sharing
  • Provide data control function

---

• Data model-Used to abstractly represent and deal with the real world

  • classification

    • Conceptual model : modeling and designing the database according to the user's point of view

    • Logical model and physical model : modeling and designing from the perspective of computer system

      • Logical model: including mesh model, hierarchical model, relational model, etc.
      • Physical model: the abstraction of the lowest layer of data, describing how data is represented and accessed within the system

  • Components

    • Data structure : Describes the components of the database, and the relationship between the objects, is a description of the static characteristics of the system

    • Data operations : perform operations on instances of objects in the database, add, delete, check, etc.

    • Integrity constraints

  • The basic concepts of the conceptual model

    • Substance: things that exist objectively and can be distinguished from each other

    • Attribute: An attribute possessed by an entity is called an attribute

    • Code: an attribute set that uniquely identifies an entity

    • Domain: the value range of the attribute

    • Entity type: use entity name and attribute name set to abstract and portray similar entities

    • Entity set: a collection of entities of the same type

    • Connections: connections within and between entities

      • 1: 1-one to one
      • 1: n-one to many
      • m: n——many to many

  • Representation of conceptual models

    • ER model
      • Rectangle: solid type
      • Oval: attributes
      • Diamond: contact name

  • The most commonly used data model

    • Format the model
      • Hierarchical model: The tree structure represents the connection between entities
      • Mesh model: mesh structure
    • Relational model: Two-dimensional table format
      • Relationship: A relationship corresponds to a table
      • Tuples: one row in the table is one tuple
      • Attribute: a column in the table is an attribute
      • Master code: uniquely determine a tuple
      • Domain: Attribute value range
      • Component: an attribute value in the tuple
      • Relationship mode: a description of the relationship
    • Object-oriented model
    • Object-relational model
      End