sample exam-114-ANSWERS

sample exam-114-ANSWERS - 1...

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1. Explain multivalued attributes, and provide an example. How are multivalued  attributes indicated in the Chen model? How are they indicated in the Crow’s  Foot model? 2. What is a weak relationship? Provide an example. 3. What steps are involved in the conversion to third normal form? 4. Explain the BCNF. How is it related to other normal forms? 5. In what two cases are composite primary keys particularly useful? 6. Explain what a relationship is and list the different types of relationships 7. What is meant by a derived attribute? Illustrate by giving at leas t one example 8. What is meant by a A single-valued attribute? Illustrate by giving an example 9. Explain the meaning of a transaction in DBMS 10. What is the purpose of Concurrency Controls? 11. List the functions or responsibilities of the DBA
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1.  Multivalued attributes are attributes that can have many values. For instance, a person may  have several college degrees, and a household may have several different phones, each with its  own number. Similarly, a car’s color may be subdivided into many colors (that is, colors for the  roof, body, and trim). In the Chen ERM, the multivalued attributes are shown by a double line  connecting the attribute to the entity. The Crow’s Foot notation does not identify multivalued  attributes.   (  (REF: 108 TOP: Critical Thinking) 2  A weak relationship, also known as a non-identifying relationship, exists if the PK of the  related entity does not contain a PK component of the parent entity. By default, relationships are  established by having the PK of the parent entity appear as an FK on the related entity. For  example, suppose that the COURSE and CLASS entities are defined as:  COURSE(CRS_CODE, DEPT_CODE, CRS_DESCRIPTION, CRS_CREDIT) CLASS(CLASS_CODE, CRS_CODE, CLASS_SECTION, CLASS_TIME, ROOM_CODE,  PROF_NUM) In this case, a weak relationship exists between COURSE and CLASS because the  CLASS_CODE is the CLASS entity’s PK, while the CRS_CODE in CLASS is only an FK. In  this example, the CLASS PK did not inherit the PK component from the COURSE entity. (REF: 113
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This note was uploaded on 02/15/2010 for the course MIT 424 taught by Professor Cevenini during the Three '10 term at Charles Sturt University.

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sample exam-114-ANSWERS - 1...

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