Presentation on theme: "Information System Analysis Lab 7. ERD entity-relationship diagram is a data modeling technique that creates a graphical representation of the entities,"— Presentation transcript:
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 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.
Components used in the creation of an ERD Relationship – Illustrates an association between two entities. It has a name which is a verb.
Crow’s foot symbol Ring represent zero Dash represent one Crow’s foot represent many
Chen and Crow’s foot notations One-to-many (1:M) relationship: a painter can paint many painting ;each painting is painted by one painter Chen notation Crow’s foot notation
Chen and Crow’s foot notations many-to-many (M:N) relationship: an Employee can learn many skills; each skill can be learned by many employees. Chen notation Crow’s foot notation
Chen and Crow’s foot notations one-to-one(1:1) relationship: an Employee can manages one store; each store is managed by one employee. Chen notation Crow’s foot notation
Chen and Crow’s foot notations
Using Visio to Draw ERD
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.
Starting a New Database Model Diagram Choose File, New, Database, Database Model Diagram
Starting a New Database Model Diagram To set the modeling options you want to use, choose Database, Options, Document