Database Design CC204 May – Aug 2017 SUBJECT TITLE DATABASE DESIGN UNIT CODE CC204 UNIT TUTOR NURHIDAYAH BT BAHAR Review Questions 1 Describe what entity types represent in an ER model and provide examples of entities with a physical or conceptual existence. Entity types are group of objects with same properties, identified by enterprise as having an independent existence. a) Physical existence - Student - Pizza - Car b) Conceptual existence - ClassEnrollment - PizzaOrder - CarPlateRegistration 2 Describe what relationship types represent in an ER model and provide examples of unary, binary, ternary, and quaternary relationships. Relationship types is the set of meaningful associations among entity types. a) Unary – Student entity which has no relationship with any other entity in ER diagram b) Binary – Customer place a pizza order c) Ternary – A staff register car owner’s details at a branch d) Quaternary – A manager view certain department’s staff’s detail at a branch 3 Describe what attributes represent in an ER model and provide examples of simple, composite, single-valued, multi-valued, and derived attributes. Attribute is the property of an entity or a relationship type. a) Simple - Attribute composed of a single component with an independent existence. Example: StudentID, UserNRIC b) Composite Attribute - Attribute composed of multiple components, each with an independent existence. Example: StudentAddress c) Single-valued Attribute - Attribute that holds a single value for each occurrence of an entity type. Example: d) Multi-valued Attribute - Attribute that holds multiple values for each occurrence of an
Database Design CC204 May – Aug 2017 entity type. Example: StudentContactNo e) Derived Attribute - Attribute that represents a value that is derivable from value of a related attribute, or set of attributes, not necessarily in the same entity type. Example: TotalStudent 4 Describe what the multiplicity constraint represents for a relationship type.
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