Entity-Relationship Model ↩

• Structure - [ Entity, Attributes, Relationship ]

• ER diagram for graphical representation.

• Entity

  • Based on real-world objects.
  • Weak entities - Depend on other entities for their existence.
  • Attributes:
    • Composite/Simple
    • Multivalued/Single-valued
    • Derived/Stored
    • Key attribute (Primary Key)\

• Relationship

  • May have Descriptive attributes, and Relationship states association between entities.
  • Relationship Set: Partial (some entities) vs Total (all entities)
  • Key constraints:
    • Mapping cardinalities (one-one, many-one, etc…)
    • Weak entities have total relationship with identifying relation

• Advanced Features

• Design Issues