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  1. 2011.02.18 Relational Database Fundamentals

Relational Database Fundamentals

Education | 2011.02.18 06:31 | Posted by 스마트 안전보건

Relational (Tables) Database Fundamentals
   * Information is everywhere in an organization   
   * Information is stored in databases 
   * Database – maintains information about
      * various types of objects (inventory),
      * events (transactions),
      * people (employees),
      * places (warehouses)   
   * Database models include: 
      * Hierarchical database model 
      * Network database model  
      * Relational database model
         * stores information in the form of logically related two-dimensional tables 

Entities and Attributes
   * Entity – a person, place, thing, transaction, or event about which information is stored 
      * The rows in each table contain the entities 
      * In Figure 6.5 CUSTOMER includes Dave’s Sub Shop and Pizza Palace entities   
   * Attribute (field, column) – characteristics or properties of an entity class 
      * The columns in each table contain the attributes 
      * In Figure 6.5 attributes for CUSTOMER include Customer ID, Customer Name, Contact Name


Keys and Relationships
Primary keys and foreign keys identify the various entities (tables) in the database 
   * Primary key – a field (or group of fields) that uniquely identifies a given entity in a table 
   * Foreign key – a primary key of one table that appears an attribute in another table and acts to provide a logical relationship among the two tables 


Relational Database Advantages
   * Increased flexibility 
   * Increased scalability and performance 
   * Reduced information redundancy 
   * Increased information integrity (quality) and information security 


Relational Database Disadvantages
   * High cost
   * Specialized staff
   * Increased vulnerability


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