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COP 4710: Database Systems (ERD Practice) Page 1 Mark Lleelly!

COP 4710: Database Systems

Fall 2010

ERD Practice Problems

Department of Electrical Engineering an Comp!ter Science

"ni#ersity of Central Floria

$nstr!ctor : Dr% &ar' (le)ellyn

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The entity type STUDENT has the followingattributes: Student_Name, Address, hone,

Age, A!ti"ity, and No_of_years# A!ti"ity

represents some !ampus$based student

a!ti"ity, and No_of_years represents the

number of years the student has engaged in

this a!ti"ity#

A gi"en student may engage in more than one

a!ti"ity#

Scenario 1

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ERD For Scenario 1

Oler Style ER 5otation

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5e) Style ERD For Scenario 1

Deri#e attrib!te

Simple attrib!tes

6ey attrib!te

&!lti/#al!e attrib!te

Composite attrib!te

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A !ompany has a number of employees# The attributes of

E%&'(EE in!lude Emp_)D *identifier+, Name, Address, andirthdate#

The !ompany also has se"eral pro-e!ts# Attributes of .'/E0Tin!lude ro-_)D *identifier+, ro-_Name, and Start_Date#

Ea!h employee may be assigned to one or more pro-e!ts, or maynot be assigned to any pro-e!t#

A pro-e!t must ha"e at least one employee assigned to it, andmay ha"e any number of employees assigner to it#

An employee1s billing rate may "ary by pro-e!t, and the!ompany wishes to re!ord the appli!able billing rate*illing_.ate+ for ea!h employee when assigned to a parti!ular

pro-e!t#

Scenario 2

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ERD For Scenario 2

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5e) Style ERD For Scenario 2

ttrib!te of te

relationsip

Optionalparticipation%

5ot e#ery

employee )or's on

a pro8ect%

&anatory

participation%

E#ery pro8ect m!st

a#e an employee %

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A uni"ersity has a large number of !ourses in its

!atalog#

Attributes of 0'U.SE in!lude 0ourse_num*identifier+, 0ourse_Name, and 0redit_2rs#

Ea!h !ourse may ha"e one or more different !oursesas prere3uisites, or may ha"e no prere3uisites#

Similarly, a parti!ular !ourse may be a prere3uisite for

any number of !ourses, or may not be a prere3uisitefor any other !ourse#

Scenario ,

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ERD For Scenario ,

Credit_hrs

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5e) Style ERD For Scenario ,

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A uni"ersity !ourse may ha"e one or more s!heduled

se!tions, or it may not ha"e a s!heduled se!tion#

Attributes of 0'U.SE in!lude 0ourse_)D*identifier+, 0ourse_Name, and 0redit_2rs#

Attributes of SE0T)'N in!lude Se!tion_Number andSemester_)D# Semester_)D is !omposed of two parts:Semester and (ear# Se!tion_Number is an integer thatdistinguishes one se!tion from another for the same

!ourse but it does not uni3uely identify a se!tion#

Scenario 4

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ERD For Scenario 4

Section )as moele as a )ea' entity% $t co!l

a#e been moele as a m!lti/#al!e attrib!te of

co!rse. o)e#er. tis moel allo)s a section of a

co!rse to a#e a relationsip )it anoter entity

9tin' instr!ctor or st!ent;te m!lti/#al!e

attrib!te case )o!l not allo) tis relationsip%

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5e) Style ERD For Scenario 4

Section )as moele as a )ea' entity% $t co!l

a#e been moele as a m!lti/#al!e attrib!te of

co!rse. o)e#er. tis moel allo)s a section of a

co!rse to a#e a relationsip )it anoter entity

9tin' instr!ctor or st!ent;te m!lti/#al!e

attrib!te case )o!l not allo) tis relationsip%

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A laboratory has se"eral !hemists who wor4 on one or more pro-e!ts#

0hemists may also use !ertain 4inds of e3uipment on ea!h pro-e!t#Attributes of 02E%)ST in!lude Employee_)D *identifier+, Name, andhone_no#

Attributes of .'/E0T in!lude ro-e!t_)D *identifier+ and Start_Date#

Attributes of E5U)%ENT in!lude Serial_no# and 0ost#

The organi6ation wants to re!ord Assign_Date 7 that is, the date whena gi"en e3uipment item was assigned to a parti!ular !hemist wor4ingon a spe!ified pro-e!t#

A !hemist must be assigned to at least one pro-e!t and one e3uipmentitem#

A gi"en pie!e of e3uipment need not be assigned, and a gi"en pro-e!tneed not be assigned either a !hemist nor a pie!e of e3uipment#

Scenario an

PRO?EC> o not nee to

participate in anyassignments% ll entities

can a#e m!ltiple

assignments%

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ro-e!ts )n!#, is an engineering firm with appro8imately 9 employees# A database is re3uired to4eep tra!4 of all employees, their s4ills, assigned pro-e!ts, and departments in whi!h they wor4# E"ery employee has a uni3ue number assigned by the firm, a name, and date of birth# )f anemployee is married to another employee of the firm, the data of the marriage and who is married

to whom must be stored; howe"er, no re!ord of marriage is re3uired if an employee1s spouse is notalso an employee# Ea!h employee has a -ob title# Ea!h employee does only one type of -ob at atime, and we only need to retain information about an employee1s !urrent -ob#

There are or ea!h !ity, we are interested in its state and

population#

An employee !an ha"e many s4ills, but they !an use only a gi"en set of s4ills on a parti!ular

pro-e!t# Employees use ea!h s4ill that they posses in at least one pro-e!t# Ea!h s4ill is assigned anumber, and we will re!ord a short des!ription of ea!h s4ill#

ro-e!ts are distinguished by pro-e!t numbers and we must store the estimated !ost of ea!h pro-e!t#

Scenario -

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ERD For Scenario -

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5e) Style ERD For

Scenario -

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Ea!h semester, ea!h student must be assigned an ad"isor who

!ounsels students about degree re3uirements and helps thestudents register for !lasses#

Ea!h student must register for !lasses with the help of anad"isor, but if the student1s assigned ad"isor is not a"ailable, the

student may register with any ad"isor# =e must 4eep tra!4 of students, the assigned ad"isor for ea!h,

and the name of the ad"isor with whom the student registerd forthe !urrent term#

Scenario 7

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ERD For Scenario 7

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5e) Style ERD For Scenario 7