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  1. 1. Punjab College Of Technical EducationPresentation On:- College Website
  2. 2. E-R Model E-R Model: Entities. Attributes. Relationship. Steps to form E-R Model: Identify Entities. Find Relationship. Draw rough E-R. Fill the cardinality. Define Primary key. Draw key based ERD. Identity Attributes. Map Attributes. Draw full attribute of ERD. Check Result.
  3. 3. • Store Information in Systematic Manner• Reduce the Problem of End-user• Easy to Store an Retrieval• Track the Information
  4. 4. Users• Different users can access data• Depending on their degree of expertise users are classified in the following groups – Naïve Users (ATM user) – Online Users – Application Programmers – Sophisticated Users – DBA
  5. 5. Entity Relationship Model• Entity – It is anything real or abstract about which we want to store the data .• Relationship – It specifies the association that exists between one or more entities.• Attribute – It is the characteristic which is common to all or most instances of particular entity.
  6. 6. Dependencies What is Dependencies? Types of Dependencies Partial key Dependencies. Primary key Dependencies. Transitive key Dependencies. Functional key Dependencies.
  7. 7. Generalization
  8. 8. Specialization StudentGrad Student Post Grad Student
  9. 9. Normalization• It is a process during which redundant relation schemas are decomposed by breaking up their attributes in to smaller relation schemas that possess desirable properties.1. First N/F2. Second N/F3. Third N/F4. BNC N/F
  10. 10. Normalization Form BC N/F Third N/F Second N/F Eliminate First N/F Eliminate Functional Transitive key dependency Removing dependency Partial keyEliminate dependencyRepeatingGroups
  11. 11. Attributes• Characteristics of entities• Domain is set of possible values• Primary keys underlined
  12. 12. Relationships • Association between entities • Connected entities are called participants • Operate in both directions • Connectivity describes relationship classification – 1:1, 1:M, M:N • Cardinality – Expresses number of entity occurrences associated with one occurrence of related entity12
  13. 13. Comparison of E-R Modeling Symbols Figure 3.3613
  14. 14. 14
  15. 15. Employee Table15
  16. 16. Student Table16
  17. 17. Completed ERD17
  18. 18. Keys• Candidate Key – A minimal set of attributes that uniquely identifies a tuple• Primary Key – The candidate key chosen as the identifying key of the relation• Alternate Key – Candidate keys which are not primary keys
  19. 19. • Foreign Key – An attribute (or set of attributes) in table R1 which also occurs as the primary key of relation R2. – R2 is called the referenced relation. – Foreign keys are also called connection keys or reference attributes.
  20. 20. Database vs. File Systems Figure 1.620
  21. 21. DFD Zero LevelStudent Teacher WebSite Course Database Department
  22. 22. Level 1Student TeacherStudent result assignment Teacher T.T Teacher tableStudent Table Teacher Table WEBSITE DATABASECourse Table Department Table Course Department Table
  23. 23. ER Of Student
  24. 24. Department + Course
  25. 25. Class With Professors(Plus Project Or Assignment)
  26. 26. ER Relationship
  27. 27. Contd…
  28. 28. BY HASH Generatio