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DBMS UNIT1
- 6. Entity-Relationship (E-R) Model COURSE # CTITILE PROF SCHED ROOM COURSE ENROLL STUDENT STUID SNAME MAJOR CREDITS GRADE
- 7. Class Hierarchies Employees ssn name lot ISA Hourly Emps Contract Emps Hourly wage Hours worked contractid * Sometimes it’s natural to classify the entities in an entity set into subclass, then we will use Class Hierarchies.
- 8. Aggregation name ssn lot Employees monitors until since Sponsors Department Projects pid Started-on pbudget dname did budget * A relationship set is an association between entity sets. Sometimes we have to model a relationship between a collection of entities and relationships, then we need to use aggregation .
- 12. TERNARY RELATIONSHIP Works_In Employees Department Locations Ternary relationship : is an associate of 3 entities sets . * Entity set = * Relation = ssn name lot did dname budget cap add * Attribute =
- 13. QUARTERY RELATIONSHIP Employees Works_In Locations Department Product Quartery relationship : is an associate of 4 entities sets. * Entity set = * Relation = * Attribute =
- 16. An example of Key Constraints on Manage Manages Department Employees ssn name lot Since dname did budget ssn = Social Security Number. did = Department id.
- 18. Weak Entities A weak entity : is an entity of which is existence depends on other entities. Policy Department Employees ssn name lot cost Pname --------- age
- 21. Entity versus Attribute Works-In2 Department Employees ssn name lot from dname did budget to * Entity set = * Relation = * Attribute =
- 22. Entity versus Relationship Manages Department Employees ssn name apptnum did budget dname Mgr-Appts lot since dbudget
- 23. Binary versus Ternary Relationship Covers Dependents Employees ssn name Pname --------- age Policies lot policyid cost
- 24. Using a Ternary Relationship instead of Aggregation Sponsors Departments Projects pid Started-on did budget pbudget dname Employees name ssn lot
- 25. ONE TO MANY RELATIONSHIP customer customer-name customer-city customer-id borrower customer-street loan loan-number amount
- 26. MANY TO ONE RELATIONSHIP customer customer-name customer-city customer-id borrower customer-street loan loan-number amount
- 27. ONE TO ONE RELATIONSHIP customer customer-name customer-city customer-id borrower customer-street loan loan-number amount
- 28. E-R Diagram with Composite, Multivalued, and Derived Attributes Customer date-of-birth phone-number name customer-id first-name age last-name middle-name zip-code state city address street Street-number apartment-number street-name
- 44. Example: Drinkers Have Favorite Beers name addr license name manf name addr Beers Drinkers Bars Serves Frequents Likes Favorite