Entity-Relationaship diagram for practice
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- 3. Objectives 3 How to use Entity–Relationship (ER) modeling in database design. Basic concepts associated with ER model. Diagrammatic technique for displaying ER model using Unified Modeling Language (UML). How to identify and resolve problems with ER models called connection traps. How to build an ER model from a requirements
- 4. ER Diagram of Branch View of DreamHome 4
- 5. Concepts of the ER Model 5 Entity types Relationship types Attributes
- 6. Entity Type 6 Entity type Group of objects with same properties, identified by enterprise as having an independent existence. Entity occurrence Uniquely identifiable object of an entity type.
- 7. Examples of Entity Types 7
- 8. ER Diagram of Staff and Branch Entity Types 8
- 9. Relationship Types 9 Relationship type Set of meaningful associations among entity types. Relationship occurrence Uniquely identifiable association, which includes one occurrence from each participating entity type.
- 10. Semantic Net of Has Relationship Type 10
- 11. ER Diagram of Branch Has Staff Relationship 11
- 12. Relationship Types 12 Degree of a Relationship Number of participating entities in relationship. Relationship of degree: two is binary; three is ternary; four is quaternary.
- 13. Binary Relationship called POwns 13
- 14. Ternary Relationship called Registers 14
- 15. Quaternary Relationship called Arranges 15
- 16. Relationship Types 16 Recursive Relationship Relationship type where same entity type participates more than once in different roles. Relationships may be given role names to indicate purpose that each participating entity type plays in a relationship. 1 to 1 1 to many ( one student applied many car pass) Many to many (Student and enrolled subject)
- 17. Recursive Relationship called Supervises with Role Names 17
- 18. Entities associated through two distinct Relationships with Role Names 18
- 19. Video streaming system (SouthernTube) 19 Student ID(PK) Name Email phoneNo Video ID (PK) Title Description Keyword DateTime StudentID status 1..1 0..* has Like ID VideoID StudentID CommentID DateTime Comment ID VideoID StudentID Content DateTime
- 20. Attributes 20 Attribute Property of an entity or a relationship type. Attribute Domain Set of allowable values for one or more attributes.
- 21. Attributes 21 Simple Attribute Attribute composed of a single component with an independent existence. Composite Attribute Attribute composed of multiple components, each with an independent existence.
- 22. Attributes 22 Single-valued Attribute Attribute that holds a single value for each occurrence of an entity type. Multi-valued Attribute Attribute that holds multiple values for each occurrence of an entity type.
- 23. Attributes 23 Derived Attribute Attribute that represents a value that is derivable from value of a related attribute, or set of attributes, not necessarily in the same entity type.
- 24. Keys 24 Candidate Key Minimal set of attributes that uniquely identifies each occurrence of an entity type. Primary Key Candidate key selected to uniquely identify each occurrence of an entity type. Composite Key A candidate key that consists of two or more attributes.
- 25. ER Diagram of Staff and Branch Entities and their Attributes 25
- 26. Entity Type 26 Strong Entity Type Entity type that is not existence-dependent on some other entity type. Weak Entity Type Entity type that is existence-dependent on some other entity type.
- 27. Strong Entity Type called Client and Weak Entity Type called Preference 27
- 28. Relationship called Advertises with Attributes 28
- 29. Structural Constraints 29 Main type of constraint on relationships is called multiplicity. Multiplicity - number (or range) of possible occurrences of an entity type that may relate to a single occurrence of an associated entity type through a particular relationship. Represents policies (called business rules) established by user or company.
- 30. Structural Constraints 30 The most common degree for relationships is binary. Binary relationships are generally referred to as being: one-to-one (1:1) one-to-many (1:*) many-to-many (*:*)
- 31. Semantic Net of Staff Manages Branch Relationship Type 31
- 32. Multiplicity of Staff Manages Branch (1:1) Relationship Type 32
- 33. Semantic Net of Staff Oversees PropertyForRent Relationship Type 33
- 34. Multiplicity of Staff Oversees PropertyForRent (1:*) Relationship Type 34
- 35. Semantic Net of Newspaper Advertises PropertyForRent Relationship Type 35
- 36. Multiplicity of Newspaper Advertises PropertyForRent (*:*) Relationship 36
- 37. Structural Constraints 37 Multiplicity for Complex Relationships Number (or range) of possible occurrences of an entity type in an n-ary relationship when other (n-1) values are fixed.
- 38. Semantic Net of Ternary Registers Relationship with Values for Staff and Branch Entities Fixed 38
- 39. Multiplicity of Ternary Registers Relationship 39
- 40. Summary of Multiplicity Constraints 40
- 41. Structural Constraints 41 Multiplicity is made up of two types of restrictions on relationships: cardinality and participation. Cardinality Describes maximum number of possible relationship occurrences for an entity participating in a given relationship type. Participation Determines whether all or only some entity occurrences participate in a relationship.
- 42. Multiplicity as Cardinality and Participation Constraints 42
- 43. Problems with ER Models 43 Problems may arise when designing a conceptual data model called connection traps. Often due to a misinterpretation of the meaning of certain relationships. Two main types of connection traps are called fan traps and chasm traps.
- 44. Problems with ER Models 44 Fan Trap Where a model represents a relationship between entity types, but pathway between certain entity occurrences is ambiguous. Chasm Trap Where a model suggests the existence of a relationship between entity types, but pathway does not exist between certain entity occurrences.
- 45. An Example of a Fan Trap 45
- 46. Semantic Net of ER Model with Fan Trap 46 At which branch office does staff number SG37 work?
- 47. Restructuring ER Model to Remove Fan Trap 47
- 48. Semantic Net of Restructured ER Model with Fan Trap Removed 48 SG37 works at branch B003.
- 49. An Example of a Chasm Trap 49
- 50. Semantic Net of ER Model with Chasm Trap 50 At which branch office is property PA14 available?
- 51. ER Model Restructured to Remove Chasm Trap 51
- 52. Semantic Net of Restructured ER Model with Chasm Trap Removed 52
- 53. Discussion 53 GrabTaxi Holdings Pte. Ltd. (branded as simply Grab) is a transportation network company based in Singapore. In addition to transportation, the company offers food delivery services via mobile app. It operates in the Southeast Asian countries of Singapore. (From wikipedia) Design the database which provides the similar service for Grab
- 54. Assignment 1 54 Shopping Cart Create a shopping cart database ER-D based on Lazada as case studies.
Editor's Notes
- #1: ERD SQL Normalization
- #2: Logical
- #17: Like C2C e-commerce customer sell products to customers
- #20: Gender – M or F Quantity – 0-1000
- #24: Integrity in chapter 2 Student (ID, Name, IC , email, phone, address, gender………) candidate key are ID, IC and email Primary key select from candidate key is ID Composite key (phone+address) We defined ID, IC and email as index Search student info, but I didn’t know the studentID, I can search by email. Searching purpose
- #40: One student have 0….2 car pass