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Dbms basic concepts12/10/2023 ![]() You can illustrate an attribute with an oval shape in an ER diagram. Unlike school, the classroom is a weak entity because it does not have any primary key and the room number here acts only as a discriminator.Īn attribute exhibits the properties of an entity. In the example below, school is a strong entity because it has a primary key attribute - school number. You showcase the weak entity as a double rectangle in ER Diagram. ![]() It showcases an entity as a rectangle in an ER diagram.įor example, in a student study course, both the student and the course are entities.Īn entity that makes reliance over another entity is called a weak entity You base an ER Diagram on three basic concepts:Īn entity can be either a living or non-living component.
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