SDB101 » Relational Model
 
  • Relational model is based on set theory
  • Main concepts
    •
    • Enumerates columns, identifies primary key and foreign keys
    • Primary Key :
      • One or more attributes uniquely identify each row within a table
    • Foreign keys:
      • R’s attributes which form primary key of another relation S
      • Value of a foreign key in any tuple of R match values in some row of S
  • Comparison to concepts in conceptual data model
    • Relations are similar to but not identical to entities
    • Domains are similar to attributes
    • Translation rules establishing exact correspondence
  • Relational model restricts attribute domains
    • simple atomic values
    • complex values for columns are not allowed
    • complex values are decomposed into simpler domains

Última modificación: Wednesday, 16 de November de 2005, 18:45