ER Model - United States Naval Academy€¦ · ER Model Entities, attributes, identifiers HAS-A...
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1 1 IT420: Database Management and Organization ER Model: part 2 13 January 2006 Adina Crăiniceanu www.cs.usna.edu/~adina 2 ER Model Entities, attributes, identifiers HAS-A Relationships Degree: binary, ternary Maximum cardinality Minimum cardinality Weak entities ID-dependent entities; identifying relationships IS-A Relationships Inclusive, Exclusive 3 Goals of This Lecture Create ER model from user requirements
Transcript of ER Model - United States Naval Academy€¦ · ER Model Entities, attributes, identifiers HAS-A...
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IT420: Database Management and Organization
ER Model: part 2 13 January 2006
Adina Crăiniceanuwww.cs.usna.edu/~adina
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ER Model
Entities, attributes, identifiersHAS-A Relationships
Degree: binary, ternaryMaximum cardinalityMinimum cardinality
Weak entities ID-dependent entities; identifying relationships
IS-A RelationshipsInclusive, Exclusive
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Goals of This Lecture
Create ER model from user requirements
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ERwin Symbol Summary
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ERwin Symbol Summary (Continued)
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Forms, Reports and ER Model
User input: FormsReportsDiscussions
DB modeler: Entity-Relationship modelSame entities, relationships under the surface
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1:1 Strong Entity Relationships
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1:1 Strong Entity Relationships
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1:N Strong Entity Relationships
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1:N Strong Entity Relationships
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N:M Strong Entity Relationships
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N:M Strong Entity Relationships
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N:M Strong Entity Relationships
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The Association Pattern
Price column
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Association Class
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Entity vs. Attribute
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Multi-valued Attribute Entity
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Recursive Relationships
Recursive relationship: an entity has a relationship to itself
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1:N Recursive Relationship
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1:1 Recursive Relationship
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N:M Recursive Relationship
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Class Exercise
Draw ER diagram for a database used to manage IT420 class (at least 3 entities)
Specify entities, attributes, identifiersSpecify relationshipsSpecify cardinalities for relationships
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Highline University
The Highline University [HU] database will track such entities as:
CollegesDepartmentsFacultyStudents
We have gathered a set of HU reports that will be the source documents for a data model
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The College Report
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Data Model from the College Report
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The Department Report
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The DEPARTMENT / PROFESSOR Relatioship:Alternate Model 1: Using a 1:N Relationship
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The DEPARTMENT / PROFESSOR Relatioship:Alternate Model 1: Using a 1:N Relationship
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The DEPARTMENT / PROFESSOR Relatioship:Alternate Model 2: Using an N:M Relationship
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The DEPARTMENT / PROFESSOR Relatioship:Alternate Model 3: Using an Association Pattern
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The DEPARTMENT / PROFESSOR Relatioship:Alternate Model 4: Using a Association Patternand a 1:N Relationship
Chaired By /Chairs
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The Department Major Report
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Data Model with STUDENT Entity
Chaired By /Chairs
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The Student Acceptance Letter
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Data Model with Advises Relationship
Chaired By /Chairs
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Final Data Model
Chaired By /Chairs
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ER Modeling: Case StudyDrugwarehouse.com has offered you a free life-time supply of prescription drugs (no questions asked) if you design its database schema. Given the rising cost of health care, you agree. Here is the information that you gathered:Patients are identified by their SSN, and we also store their names and ageDoctors are identified by their SSN, and we also store their names and specialtyEach patient has one primary care physicianEach doctor has at least one patientDoctors prescribe drugs for patients
