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Information System Analysis Lab 7

Information System Analysis Lab 7. ERD. entity-relationship diagram is a data modeling  technique that creates a graphical representation of the entities, and the relationships between entities. Components used in the creation of an ERD.

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Information System Analysis Lab 7

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  1. Information System Analysis Lab 7

  2. ERD • entity-relationship diagram is a data modeling  technique that creates a graphical representation of the entities, and the relationships between entities.

  3. Components used in the creation of an ERD • Entity – A person, place or thing about which we want to collect and store multiple instances of data. It has a name, which is a noun, and attributes which describe the data we are interested in storing. It also has an identifier.

  4. Components used in the creation of an ERD • Relationship – Illustrates an association between two entities. It has a name which is a verb.

  5. Crow’s  foot symbol Ring represent zero Dash represent one Crow’s  foot represent many

  6. Chen and Crow’s foot notations One-to-many (1:M) relationship: Crow’s foot notation Chen notation a painter can paint many painting ;each painting is painted by one painter

  7. Chen and Crow’s foot notations many-to-many (M:N) relationship: Crow’s foot notation Chen notation an Employee can learnmany skills; each skill can be learned by many employees.

  8. Chen and Crow’s foot notations one-to-one(1:1) relationship: Crow’s foot notation Chen notation an Employee can manages one store; each storeis managed by oneemployee.

  9. Chen and Crow’s foot notations

  10. Using Visio to Draw ERD

  11. A student fills a seat. This is a 1:1 relationship. 1 student can fill a maximum of 1 seat. 1 seat can be filled by a maximum of 1 student. • A student takes a course. This is a M:M relationship. One student can take many courses, and one course can be taken by many students. -a student must take at least one course, and a course must be taken by at least one student. • An instructor teaches a course. This is a 1:M relationship. One instructor can teach many courses, but one course can only be taught by one instuctor. – an instructor must teach at least 1 course, and a course must be taught by 1 instructor.

  12. Starting a New Database Model Diagram • Choose File, New, Database, Database Model Diagram

  13. Starting a New Database Model Diagram • To set the modeling options you want to use, choose Database, Options, Document

  14. Format  line

  15. ERD Using Visio

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