Data Base week6_3

03/03/2010

 

Preparation for exam

• 
  
  Scenario
  
  • ER Diagram
    
  • Data dictionary
    
  • 
    
    Table definition
    
    
    
    
• 
  
  Normalisation (Explain using example table)
  
  • 
    
    Insert Anomaly
    
    • If a new student enrols, their data have to be inserted without grade or some data.
      
  • 
    
    Modification Anomaly
    
    • If Cooke's email address is changed, we have to change this data 2 times. So, typing miss may be occurred.
      
  • 
    
    Deletion Anomaly
    
    • 
      
      If Lau quits this school, we will lose vital data.
      
      
      
      
  • 
    
    Functional Dependency (X → Y)
    
    • StudentID - StudentName
      
    • StudentID - StudentEmail
      
    • ClassID - ClassName
      
    • StudentID, ClassID - Grade
      
  • 
    
    Transitive Dependency (A→B, B→C, Thus A→C)
    
    • 
      
      ClassID - TermID - Term
      
      
      
      
  • 
    
    Entity Integrity
    
    • Every table must have primary key and the primary key must be unique
      
  • 
    
    Referential Integrity
    
    • Referential Integrity means if you use foreign key, the primary key, which is referred by the foreign key, must be exist in the original table.