Entity Relationship Diagrams :Entity Relationship Diagrams Don Archer


Entity Relationship Diagram :Entity Relationship Diagram ERDs – depicts data in terms of the entities and relationships described by the data.


Entity Definition :Entity Definition Entity - 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 :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 :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 Relationships :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 :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 :Identifying Entities & Relations


Identifying Entities :Identifying Entities X Many-to-many


Identifying Entities :Identifying Entities X Enrolls in Consists of Associative Entity


Slide 13:Is This Correct???


Slide 14:NO! Many-to-many This is a many-to-many relationship


Slide 15:X How do you fix a M:M relation?


Slide 16:Associative Entity


Slide 17:Refinements


Slide 18:Refinements


Slide 19:Refinements


Slide 20:Location & Faculty


Slide 24:Recursive


Business rules :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 :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 :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.


Slide 28:Visio


Other Questions? :Other Questions?