Chapter 3 Data Modeling Using the Entity-Relationship Modeling

Transcription

1 Chapter 3 Data Modeling Using the Entity-Relationship Modeling Multiple-Choice Questions: 1) is an object modeling methodology. a) EML b) UML c) OML d) DML 2) diagrams are important part of object modeling methodology. a) application b) data c) class d) level 3) During the design phase of database design, the properties of data is given importance, rather than its storage details. a) conceptual b) logical c) physical d) actual 4) is the basic object of ER model which is a thing in real world. a) relation b) domain c) attribute d) entity 5) Entities are described by properties called as. a) attributes b) characteristics c) features d) relations 6) Attributes that are not divisible are called. a) composite b) atomic c) complex d) structured 7) attributes can have more than one value. a) composite b) simple c) multi-valued d) single valued 8) When the value of an attribute A is obtained from the value of an attribute B, then the attribute A is called. a) composite b) stored c) derived d) retrieved 9) The entity types are represented in ER-diagrams by. a) ovals b) rectangles c) double ovals d) diamonds 10) The multivalued attributes are represented in ER-diagrams by. a) ovals b) rectangles c) double ovals d) diamonds 11) attribute values are used to identify each entity uniquely. a) complex b) unique c) characters d) key 12) An entity type without a key attribute is called entity type. a) null b) weak c) strong d) single 13) specifies the set of values that can be assigned to the attribute. a) block b) relation c) structure d) domain 14) Multivalued attributes are shown by. a) ( ) b) { } c) < > d) 15) The relationships are displayed as in ER-diagrams. a) rectangles b) ovals c) triangles d) diamonds

2 16) The relationship in which an entity type participates more than once is a relationship. a) recursive b) iterative c) enumerated d) implied 17) specifies the maximum number of relationship instances that an entity can participate. a) range b) domain c) cardinality d) ceiling 18) In ER diagrams, the total participation is displayed as a. a) oval b) single line c) double line d) arrow 19) A weak entity type normally has a key. a) partial b) total c) super d) strong 20) A weak entity type always has a participation constraint with respect to its identifying relationships. a) partial b) total c) overlap d) disjoint 21) The partial key attribute is underlined with a line. a) single b) shaded c) dotted d) double TRUE or FALSE: 1. The ER model is high-level conceptual model. ( T / F ) 2. The class diagrams in UML specify the operations on objects also. ( T / F ) 3. In database design the conceptual design phase comes after logical design phase. ( T / F ) 4. Composite attributes cannot be further subdivided. ( T / F ) 5. A multivalued attribute can have lower and upper bounds. ( T / F ) 6. An attribute value can be derived from another attribute. ( T / F ) 7. The names on entity types and entity sets are different. ( T / F ) 8. An entity cannot have more than one key attribute. ( T / F ) 9. A relationship type of degree two is called as ternary relationship. ( T / F ) 10. Relationship types can also have attributes. ( T / F ) 11. The attribute of a relationship type can be added to participating entity types. ( T / F ) 12. A weak entity type can have more than one identifying entity type. ( T / F ) 13. The number of levels of weak entity types cannot be more than one. ( T / F ) Short Answer Questions: 1. What are the main phases of database design? Write them in order. Ans. Requirement collection & analysis, conceptual design, logical design and physical design. 2. How does ER model describes data? Ans. ER model describes data as entities, relationships, attributes 3. What are the different values a null value can have? Ans. A Null value can mean an unknown, not applicable, exists but not available.

3 Match the following notations for ER diagrams: Symbol Meaning MULTIVALUED ATTRIBUTE DERIVED ATTRIBUTE IDENTIFYING RELATIONSHIP ENTITY ATTRIBUTE WEAK ENTITY RELATIONSHIP KEY ATTRIBUTE PARTIAL KEY COMPOSITE ATTRIBUTE

4 Identify the cardinality ratios and participation constraints of the following binary relationships: e1 e2 e3 e4 e5 e6 EMPLOYEE e1 e2 e3 e4 e5 e6 EMPLOYEE e1 e2 e3 e4 e5 e6 EMPLOYEE e1 e2 e3 e4 e5 e6 EMPLOYEE r1 r2 r3 r4 r5 r6 WORKS_ON r1 r2 r3 r4 r5 r6 MANAGES r1 r2 r3 r4 r5 r6 WORKS_ON r1 r2 r3 r4 r5 r6 MANAGES d1 d2 d3 d4 d5 d6 PROJECT d1 d2 d3 d4 d5 d6 DEPARTMENT d1 d2 d3 d4 d5 d6 PROJECT d1 d2 d3 d4 d5 d6 DEPARTMENT Select the cardinality ratio: 1 : 1 1 : N N : 1 M : N Participation of EMPLOYEE: Participation of PROJECT: Select the cardinality ratio: 1 : 1 1 : N N : 1 M : N Participation of EMPLOYEE: Participation of DEPARTMENT: Select the cardinality ratio: 1 : 1 1 : N N : 1 M : N Participation of EMPLOYEE: Participation of PROJECT: Select the cardinality ratio: 1 : 1 1 : N N : 1 M : N Participation of EMPLOYEE: Participation of DEPARTMENT:

5 In the ER diagram for COMPANY database identify the following: 1. Names of (nonweak) entity types 2. Names of weak entities 3. Key of DEPARTMENT 4. Primary key of EMPLOYEE 5. Names of partial keys (if any) 6. Names of composite attributes 7. Names of multivalued attributes 8. Names of relationships 9. Names of identifying relationships 10. Names of derived attributes Answer the following questions based on the ER diagram for COMPANY database: 1. All the EMPLOYEEs must work on some PROJECT. ( T / F ) 2. All the EMPLOYEEs should have a DEPENDENT. ( T / F ) 3. All the DEPARTMENTs should have a PROJECT. ( T / F ) 4. An EMPLOYEE need not be a manager of a DEPARTMENT. ( T / F ) 5. A DEPARTMENT need not be managed by an EMPLOYEE. ( T / F ) Answer the following questions based on the ER diagram for COMPANY database: 1. One EMPLOYEE can have many DEPENDENT s. ( T / F ) 2. One EMPLOYEE can work on a single PROJECT. ( T / F ) 3. One DEPARTMENT can control many PROJECTs. ( T / F ) 4. One PROJECT can belong to only one DEPARTMENT. ( T / F ) 5. One EMPLOYEE can work for many DEPARTMENTs. ( T / F ) 6. One PROJECT can be done by only one EMPLOYEE. ( T / F ) 7. One EMPLOYEE can supervise only one EMPLOYEE. ( T / F ) 8. One DEPARTMENT is managed by only one EMPLOYEE. ( T / F ) 9. One DEPARTMENT can have many EMPLOYEEs. ( T / F ) 10. One EMPLOYEE can manage many DEPARTMENTs. ( T / F )

6 Answer the following questions based on the ER diagram for COMPANY database: 1. The attribute NumberOFEmployees of DEPARTMENT entity is a attribute. 2. The attribute Name of EMPLOYEE entity is a attribute. 3. The attribute Locations of DEPARTMENT entity is a attribute. 4. The attribute Name of DEPENDENT entity is a key. 5. The attribute Name of PROJECT entity is a key. 6. The attribute Ssn of EMPLOYEE entity is a key. 7. The relationship DEPENDENTS_OF is a relationship. a) identifying b) recursive c) strong d) weak 8. The relationship SUPERVISION is a relationship. a) identifying b) recursive c) strong d) weak 9. The attribute Name of PROJECT entity is a attribute. a) simple b) derived c) composite d) multivalued 10. The entity DEPENDENT is a entity. a) weak b) good c) strong d) super

7 In the ER diagram for AIRLINE database identify the following: 1. Names of (nonweak) entity types 2. Names of weak entities 3. Key of AIRPORT 4. Primary key of AIRPLANE 5. Names of partial keys (if any) 6. Names of composite attributes 7. Names of multivalued attributes 8. Names of relationships 9. Names of identifying relationships 10. Names of derived attributes Answer the following questions based on the ER diagram for AIRPLANE database shown below: 1. The attribute NumberOFAirplanes of AIRPLANE entity is a attribute. 2. The attribute CustomerName of RESERVATION entity is a attribute. 3. The attribute Weekdays of FLIGHT entity is a attribute. 4. The attribute SeatNo of SEAT entity is a key. 5. The attributes Number and Airline of FLIGHT entity is a key. 6. The attribute AirplaneId of AIRPLANE entity is a key. 7. The relationship INSTANCE OF is a relationship. a) identifying b) recursive c) strong d) weak 8. The entity FLIGHT LEG is a entity. a) weak b) good c) strong d) super 9. The attribute State of AIRPORT entity is a attribute. a) simple b) derived c) composite d) multivalued 10. The entity FLIGHT is a entity. a) weak b) good c) strong d) super

8 Answer the following questions based on the ER diagram for AIRLINE database: 1. One AIRPLANE TYPE can have only one AIRPLANE. ( T / F ) 2. One AIRPLANE TYPE can land in only one AIRPORT. ( T / F ) 3. One AIRPORT can allow landing of many AIRPLANE TYPEs. ( T / F ) 4. One FLIGHT can have many FAREs. ( T / F ) 5. One AIRPLANE can be assigned many LEG INSTANCEs. ( T / F )

9 In the following ER diagram for BANK database identify the following: 1. Names of (nonweak) entity types 2. Names of weak entities 3. Key of BANK 4. Primary key of CUSTOMER 5. Names of partial keys (if any) 6. Names of composite attributes 7. Names of multivalued attributes 8. Names of relationships 9. Names of identifying relationships 10. Names of derived attributes Answer the following questions based on the ER diagram for BANK database shown below: 1. The attribute NumberOFBranches of BANK-BRANCH entity is a attribute. 2. The attribute Name of CUSTOMER entity is a attribute. 3. The attribute Type of ACCOUNT entity is a attribute. 4. The attribute BranchNo of BANK-BRANCH entity is a key. 5. The attributes LoanNo and Type of LOAN entity is a key. 6. The attribute SSN of CUSTOMER entity is a key. 7. The relationship BRANCHES is a relationship. a) identifying b) recursive c) strong d) weak 8. The entity BANK-BRANCH is a relationship. a) weak b) good c) strong d) super 9. The attribute Code of BANK entity is a attribute. a) simple b) derived c) composite d) multivalued 10. The entity CUSTOMER is a entity. a) weak b) good c) strong d) super

10 Answer the following questions based on the ER diagram for BANK database shown below: 1. One BANK can have many BRANCHES. ( T / F ) 2. One BANK-BRANCH can have only one ACCOUNT. ( T / F ) 3. One CUSTOMER can have many ACCOUNTs. ( T / F ) 4. One CUSTOMER can have only one LOAN. ( T / F ) 5. One ACCOUNT can belong to many CUSTOMERS. ( T / F )

11 Composite and multivalued attributes can be nested to any number of values. Suppose we want to design an attribute for a STUDENT entity type to keep track of previous college education. The student might have attended more than one college previously. Such an attribute will have: One entry for each college previously attended having college name, start date and end date, degree entries (can be more than one), and courses entries. Each degree entry contains a degree name, month and year the degree was awarded. Each course entry contains a course name, semester, year and grade. Design an attribute to hold this information using the notations ( ) for composite attributes and { } for multivalued attributes as well as show how it can be represented in ER diagram.

12 Consider the following set of requirements for a university database that is used to keep track of student s transcripts. The university keeps track of each student s name, student number, National ID number, current address and phone, permanent address and phone, birthdate, gender, class (I year, II year ), major department, minor department, and degree program (B.Sc., B.A.,,Ph.D.). The name of the student should have first, middle, and last names. The permanent address should have apartment number, street number, city, state, postal code. Both National ID number and student number must be unique for each student. Each department must be described by a name, department code, office number, office phone, and college. Both name and code must be unique for each department. Each course has a course name, description, course number, number of credit hours, level number, and offering department. The course number should be unique for each department. Each section has an instructor name, semester, year, course number and section number. The section number must be unique and each course can have multiple sections taught during same semester/year. A grade report has a student number, student name, section number, letter grade, and numeric grade (percentage marks). Design an ER schema for this application and draw an ER diagram for that schema. Specify key attributes for each entity type, and structural constraints on each relationship type.