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Basic Symbols

Basic Symbols. Student Entity type using E-R notation. Multivalued – Employee . Weak (attributive) entity. Example relationships of different degrees. 10. 5. Bill of Materials Unary Relationship. (a) Many-to-Many Relationship. (b) Two Instances. CA.

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Basic Symbols

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  1. Basic Symbols

  2. Student Entity type using E-R notation

  3. Multivalued – Employee

  4. Weak (attributive) entity

  5. Example relationships of different degrees 10.5

  6. Bill of Materials Unary Relationship (a) Many-to-Many Relationship (b) Two Instances

  7. CA • Consider the Is_married_to unary relationship • Assume we want to know the date on which a marriage occurred. Augment this ER diagram to include a Date_married attribute. • Since sometimes persons remarry after the death of a spouse or divorce, redraw this ERD to show the whole history of marriages for person. Show the Date_married attribute on this diagram.

  8. 1

  9. 2.

  10. Optional cardinalities

  11. Mandatory Cardinalities

  12. One optional, one mandatory cardinality

  13. 1:M Relationship(ERD)

  14. M:M Relationship(tbl)

  15. M:M Relationship(ERD)

  16. IS-A Relationships(tbl)

  17. IS-A Relationships (ERD)

  18. CA • In a real state DB, there is an entity called PROPERTY, which is a property for sale by the agency. Each time a potential property buyer makes a purchase offer on a property, the agency records the date, offering price, and name of the person making the offer. • Represent the PROPERTY entity and its purchase offer attributes using the notation for multivalued attributes. • Represent the PROPERTY entity and its purchase offer attributes using two entity types. • Finally, assume the agency decides to also keep data about buyers and potential buyers, including their name, phone number, and address. Augment your answer to part b above to accommodate this new entity type.

  19. a.

  20. b.

  21. c.

  22. CA - Draw a ER diagram for the following

  23. ERD – customer order

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