Extended E-R Model: Basic Symbols Strong Entity Set Associative Entity Set Weak Entity Set Attribute Association Relationship Set Multi-Valued Attribute Identifying Relationship Set Derived attribute

Extended E-R: Relationship Cardinality Mandatory One Mandatory Many Optional One Optional Many

Relationship Set: Cardinality Maximum Cardinality for Offering Maximum Cardinality for Course Course Has Offering (1:1) (0:N) Course-NO C-Des Credit-Hour Offer-NO Off-Location Off-Time Minimum Cardinality for Offering Minimum Cardinality for Course

Graphical Notations for Cardinality 1: One M: Many 1 M EMPLYEE DEPARTMENT Works-for : One EMPLOYEE DEPARTMENT Works-for : Many EMPLOYEE DEPARTMENT Works-for Many One EMPLOYEE : One : Many DEPARTMENT Works-for

ER Diagram: An Example Sends SUPPLIER Supplies CUSTOMER Includes SHIPMENT ITEM Submits KEY Relationship Used_in Entity Cardinalities Mandatory One Requests PRODUCT ORDER Mandatory Many Optional One Optional Many

Weak Entity: An Example Last_Name First_Name Middle_Initial Date_of_Birth Employee_Name Employee_ID Dependent_Name EMPLOYEE Has DEPENDENT

Unary Relationship: Examples Marries PERSON One-to-one Manages EMPLOYEE One-to-many

Binary Relationship: Examples EMPLOYEE Assigns PARKING PLACE One-to-One PRODUCT LINE Contains PRODUCT One-to-Many STUDENT Registers_for COURSE Many-to-Many

Ternary Relationships: Example Supplies VENDOR WAREHOUSE PART Shipping_mode Unit_cost

Composite Attribute Address City State Street_Address Postal_Code DB Design Question: Should we model address as a simple or composite attribute?

Multi-Valued versus Derived Attribute EMPLOYEE Date_Employed Years_Employed Employee_ID Employee_Name Address Skill

Specialization/Generalization Relationships: Disjointness and Completeness Constraints PERSON Overlapping and Partial Coverage IS-A (O,P) DOCTOR PATIENT Disjoint and Total Coverage IS-A (D,T) IN-PATIENT OUT-PATIENT