Chapter 4: The Mapping of E-R Model into Relational Model

Chapter 4: The Mapping of E-R Model into Relational Model

1. ENTITY MAPPING

   • Strong entity mapping
     • Derived Attribute, Primary Key Attribute, Foreign Key Attribute, Composite Attribute, Multi-valued Attribute,
   • Weak entity mapping
     • An entity whose existence is dependent on some other entity.

2. BINARY RELATIONSHIP MAPPING

   • 1:1 Binary Relationship
     • 1:1 binary relationship is converted to a single relational table
   • 1:M Binary Relationship
     • Mandatory Participating Class, Optional Participating Class
   • M:N Binary Relationship
     • M:N binary relationship is normally represented by a separate relational schema

3. RECURSIVE RELATIONSHIP MAPPING

   • The mapping concerning recursive relationship need to follow a few simple rules that had been imposed to the binary relationship mapping.

4. TERNARY RELATIONSHIP MAPPING

   • A ternary relationship involved three different entity types. Every ternary relationship is mapped into a separate relational schema that contains the primary key attribute for the three related entities together with its descriptive attributes

5. SUPERCLASS AND SUBCLASS MAPPING

   • Subclass entity can be represented by a relation that contains a key attribute of the superclass entity together with additional attributes that are specific to the subclass entity