entity relationship diagrams don archer. entity relationship diagram erds – depicts data in terms...
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Entity Relationship Diagrams
Don Archer
Entity Relationship DiagramERDs – depicts data in terms of the
entities and relationships described by the data.
Entity DefinitionEntity - is a person, place, thing, or
event of importance to the organization. Anything that can be a noun can be an entity.
Entity Occurrence - One individual instance of a type of entity - the set of data describing an instance of an entity.
Identifying Entities
Identify the nouns in the conversation:
Students may enroll in 12 courses. Classes are scheduled during 6 sessions throughout the year and are identified by sections. Each class may contain 18 students. Students may have several registrations for these classes that are held at 6 locations.
Qualified faculty are assigned to various sections of of the classes. Not all faculty are qualified to teach all courses.
Identifying Entities
Identify the nouns in the conversation:
STUDENTs may enroll in 12 COURSEs. CLASSes are scheduled during 6 SESSIONs throughout the YEAR and are identified by SECTIONs. Each CLASS may contain 18 STUDENTs. STUDENTs may have several REGISTRATIONs for these CLASSes that are held at 6 LOCATIONs.
QUALIFIED FACULTY are assigned to various SECTIONs of of the CLASSes. Not all FACULTY are qualified to teach all COURSEs.
studentidstudent nameaddresscitystatepostal codefacutlyid (FK)
STUDENT
studentidstudent nameaddresscitystatepostal codefacutlyid (FK)
STUDENT
course nocourse desccredit hours
COURSE
Identifying Relationships
Identify the verbs in the conversation:
STUDENTs may enroll in 12 COURSEs. Classes are scheduled during 6 SESSIONs throughout the YEAR and are identified by SECTIONs. Each class may contain 18 students. Students may have several REGISTRATIONs for these classes that are held at 6 LOCATIONs.
QUALIFIED FACULTY are assigned to various sections of of the classes. Not all FACULTY are qualified to teach all courses.
Identifying Relationships
Identify the verbs in the conversation:
Students may ENROLL in 12 courses. Classes are SCHEDULED during 6 sessions throughout the year and are IDENTIFIED by sections. Each class may CONTAIN 18 students. Students may HAVE several registrations for these classes that are HELD at 6 locations.
Qualified faculty are ASSIGNED to various sections of of the classes. Not all faculty are QUALIFIED to teach all courses.
Identifying Entities & Relations
studentidstudent nameaddresscitystatepostal codefacutlyid (FK)
STUDENT
course nocourse desccredit hours
COURSE
enrolls
Identifying Entities
studentidstudent nameaddresscitystatepostal codefacutlyid (FK)
STUDENT
course nocourse desccredit hours
COURSE
enrolls
Many-to-many
Identifying Entities
studentidstudent nameaddresscitystatepostal codefacutlyid (FK)
STUDENT
course nocourse desccredit hours
COURSE
enrolls
course nostudentidgrade
SCHEDULED CLASS
Enrolls inConsists of
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
consist of/makes up
registers for/registers
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
Is This Correct???
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
consist of/makes up
registers for/registers
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
NO!
Many-t
o-man
y
This is a many-to-many relationship
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
consist of/makes up
registers for/registers
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
How do you fix a M:M relation?
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
consist of/makes up
registers for/registers
has/is for
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
Associative Entity
year
YEAR
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
consist of/makes up
registers for/registers
has/is for
have/is for
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
Refinements
year
YEAR
session
SESSION
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
consist of/makes up
registers for/registers
has/is for
have/is for
have/is for
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
Refinements
year
YEAR
session
SESSION
section no
SECTION
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
consist of/makes up
registers for/registers
has/is for
have/is for
have/is for
have/is for
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
Refinements
year
YEAR
session
SESSION
section no
SECTION
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
facutlyidfaculty nameaddresscitystatezipemphasisfacutlyid/1 (FK) (IE)
FACULTY
consist of/makes up
registers for/registers
has/is for
is assigned to/has assigned
held at/hosts
have/is for
have/is for
have/is for
location codeloc description
LOCATION
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
Location
& Faculty
year
YEAR
session
SESSION
section no
SECTION
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
facutlyidfaculty nameaddresscitystatezipemphasisfacutlyid/1 (FK) (IE)
FACULTY
course nofacutlyid (FK)
QUALIFIED FACULTY
consist of/makes up
registers for/registers
has/is for
becomes/consitst of
held at/hosts
have/is for
have/is for
have/is for
location codeloc description
LOCATION
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
qualified for/qualified by
year
YEAR
session
SESSION
section no
SECTION
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
facutlyidfaculty nameaddresscitystatezipemphasisfacutlyid/1 (FK) (IE)
FACULTY
course nofacutlyid (FK)
QUALIFIED FACULTY
consist of/makes up
registers for/registers
has/is for
becomes/consitst of
is assigned to/has assigned
held at/hosts
have/is for
have/is for
have/is for
location codeloc description
LOCATION
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
qualified for/qualified by
year
YEAR
session
SESSION
section no
SECTION
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
facutlyidfaculty nameaddresscitystatezipemphasisfacutlyid/1 (FK) (IE)
FACULTY
course nofacutlyid (FK)
QUALIFIED FACULTY
consist of/makes up
registers for/registers
has/is for
advised by/advises
becomes/consitst of
is assigned to/has assigned
held at/hosts
have/is for
have/is for
have/is for
location codeloc description
LOCATION
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
qualified for/qualified by
year
YEAR
session
SESSION
section no
SECTION
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
facutlyidfaculty nameaddresscitystatezipemphasisfacutlyid/1 (FK) (IE)
FACULTY
course nofacutlyid (FK)
QUALIFIED FACULTY
mentors/is mentored by
consist of/makes up
registers for/registers
has/is for
advised by/advises
becomes/consitst of
is assigned to/has assigned
held at/hosts
have/is for
have/is for
have/is for
location codeloc description
LOCATION
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
qualified for/qualified by
Recursive
Business rules Each STUDENT may HAVE one or more CLASS REGISTRATIONS. Each CLASS REGISTRATION must be ASSIGNED to one & only one
STUDENT.
Each CLASS may HAVE one or more CLASS REGISTRATIONs. Each CLASS REGISTRATION must BE FOR one & only one CLASS.
Each COURSE may BE ASSIGNED to one or more SCHEDULED CLASSes.
Each SCHEDULED CLASS must CONSIST on one & only one COURSE.
Business rules Each LOCATION may be ASSIGNED one or more SCHEDULED
CLASSes. Each SCHEDULED CLASS must BE ASSIGNED to one & only one
LOCATION.
Each YEAR may be ASSIGNED one or more SCHEDULED CLASSes. Each SCHEDULED CLASS must BE ASSIGNED to one & only one
YEAR.
Each SECTION may be ASSIGNED one or more SCHEDULED CLASSes.
Each SCHEDULED CLASS must BE ASSIGNED to one & only one SECTION.
Business rules Each FACULTY may ADVISE one or more STUDENTs. Each STUDENT must be ADVISED BY one & only one ADVISOR.
Each QUALIFIED FACULTY must be ASSIGNED to one & only one COURSE.
Each COURSE may be QUALIFIED by one or more QUALIFIED FACULTY.
Each QUALIFIED FACULTY must CONSIST of one & only one FACULTY.
Each FACULTY may be QUALIFIED for one or more QUALIFIED FACULTY positions.
year
YEAR
session
SESSION
section no
SECTION
yearsessionsection nocourse nostudentid/1studentid (FK) (IE)
CLASS REGISTRATION
studentidstudent nameaddresscitystatepostal codefacutlyid (FK) (IE)
STUDENT
course nocourse desccredit hours
COURSE
facutlyidfaculty nameaddresscitystatezipemphasisfacutlyid/1 (FK) (IE)
FACULTY
course nofacutlyid (FK)
QUALIFIED FACULTY
mentors/is mentored by
consist of/makes up
registers for/registers
has/is for
advised by/advises
becomes/consitst of
is assigned to/has assigned
held at/hosts
have/is for
have/is for
have/is for
location codeloc description
LOCATION
yearsessionsection nocourse nofacultyidlocation code
SCHEDULED CLASS
qualified for/qualified by
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