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Chapter 5 – Part 1

Chapter 5 – Part 1. Data Modelling with the Entity-Relationship Model. Contents. A. Computer Company Problem B. Solution. A. Computer Company Problem.

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Chapter 5 – Part 1

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  1. Chapter 5 – Part 1 Data Modelling with the Entity-Relationship Model

  2. Contents A. Computer Company Problem B. Solution

  3. A. Computer Company Problem • ProgLtd is a company that places computer programmers at temporary jobs. They keep track on each programmer: the programmer's identification number, the programmer's last name, the programmer's first name, the programmer's rank (Junior, Senior ...), gender, his/her hourly rate and what languages the programmer knows. Beside, each programmer has been issued a badge which is used for enter their office. On each badge has following information: badge’s code, the programmer's identification number, issued date.

  4. ProgLtd deals with clients who may require programmers who know a particular programming language. Once a programmer is assigned a temporary job, ProgLtd would like to keep track of when he/she started the job, the total number of hours he/she is expected to spend at job and the date he/she finished the job. That is in addition to the client name and phone number where the temp has been assigned. • Let’s design DB diagram for above requirements

  5. B. Solutions • Logical Analysis • Physical Analysis

  6. 1. Logical Analysis 1.1. Indentify Entity 1.2. Indentify Attributes 1.3. Identify Primary Identifier 1.4. Identify Alternative Identifier 1.5. Identify Mandatory Attributes 1.6. Identify Relationship

  7. 1.1. Identify Entity

  8. 1.2. Identify Attributes

  9. 1.3. Identify Primary Identifier

  10. 1.4. Identify Alternative identifier

  11. 1.5. Identify Mandatory Attributes

  12. 1.6. Identify Relationship 1.6.1. Identify Maximum Cardinalities 1.6.2. Identify Minimum Cardinalities

  13. 1.6.1. Identify Maximum Cardinalities 1.6.1.1. Maximum Cardinalities Definition 1.6.1.2. Maximum Cardinalities on Diagram

  14. 1.6.1.1. Maximum Cardinalities Definition • Maximum Cardinalities is the maximum number of entity instances that can participate in a relationship. • There are three types of maximum cardinality: • One-to-One [1:1] • One-to-Many [1:N] • Many-to-Many [N:M]

  15. 1.6.1.2. Maximum Cardinalities on Diagram

  16. 1.6.2. Identify Minimum Cardinalities 1.6.2.1. Minimum Identifier Definition 1.6.2.2. Minimum Cardinalities on Diagram

  17. 1.6.2.1. Minimum Identifier Definition • is the minimum number of entity instances that must participate in a relationship. • Minimums are generally stated as either zero or one: • IF zero [0] THEN participation in the relationship by the entity is optional, and no entity instance must participate in the relationship. • IF one [1] THEN participation in the relationship by the entity is mandatory, and at least one entity instance must participate in the relationship.

  18. 1.6.2.2. Minimum Cardinalities on Diagram

  19. 2. Physical Diagram

  20. References • Database Processing – Chapter 5 • Data Modelling with the Entity-Relationship Model • David M. Kroenke

  21. ?

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