Data Modeling with ERD - ITBP340 Database Systems Chapter...

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Click to edit Master subtitle style 11 ITBP340 Database Systems Chapter 3: Data Modeling Using the Entity-Relationship Model Elarbi Badidi College of Information Technology United Arab Emirates University [email protected]
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22 In these chapter, you will learn: ü Using Data Models for Database Design ü Entity  Types,  Entity  Sets,  Attributes,  and  Keys ü Relationships,  Relationship  Types,  Roles,  and Structural Constraints
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33 Basic Modeling Concepts Models “Description  or  analogy  used  to  visualize something  that  cannot  be  directly  observed”  Webster’s Dictionary Data Model Relatively  simple  representation  of  complex real-world data structures
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44 Degrees of Abstraction Conceptual Global view of data Basis  for  identification  and  description  of  main  data items ERD used to represent conceptual data model Hardware and software independent  Internal Representation of database as seen by DBMS Adapts conceptual model to specific DBMS
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55 Degrees of Abstraction (con’t.) Physical Lowest level of abstraction Software and hardware dependent Requires definition of physical storage devices and access methods
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66 Data Models: Degrees of Data Abstraction
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77 The Entity Relationship (E-R) Model Represents conceptual view Main Components Entities Corresponds to entire table, not row Represented by rectangle Attributes Relationships
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88 Data Modeling Using the ER Model ER Diagrams- Notation Example Database Application (COMPANY) ER Model Concepts Entities and Attributes Entity Types, Value Sets, and Key Attributes Relationships and Relationship Types Weak Entity Types Roles and Attributes in Relationship Types
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99 SUMMARY OF ER-DIAGRAM NOTATION Meaning ENTITY TYPE WEAK ENTITY TYPE RELATIONSHIP TYPE IDENTIFYING RELATIONSHIP TYPE ATTRIBUTE KEY ATTRIBUTE MULTIVALUED ATTRIBUTE COMPOSITE ATTRIBUTE DERIVED ATTRIBUTE TOTAL PARTICIPATION OF E2 IN R CARDINALITY RATIO 1:N FOR E1:E2 IN R STRUCTURAL  CONSTRAINT  (min,  max)  ON  PARTICIPATION OF E IN R Symbo l E1 R E2 E1 R N E2 R (min,max ) E
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1010 Example COMPANY Database Requirements of the Company (oversimplified for illustrative purposes) The  company  is  organized  into  departments.  Each department has a name, number and an employee who manages  the  department.  We  keep  track  of  the  start date of the department manager.  Each department controls a number of projects. Each project has a name, number and is located at a single
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1111 Example COMPANY Database (Cont.) We  store  each  employee’s  social  security  number, address,  salary,  sex,  and  birthdate.  Each  employee works  for  one  department  but  may  work  on  several projects.  We  keep  track  of  the  number  of  hours  per week  that  an  employee  currently  works  on  each
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This note was uploaded on 03/26/2010 for the course ITBP 340 taught by Professor Elarabi,maulai during the Spring '10 term at United Arab Emirates University.

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Data Modeling with ERD - ITBP340 Database Systems Chapter...

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