Use template shapes: Use the scratchpad for storing groups of shapes so you don’t have to build each up from scratch. To create an associative entity in the first style of diagram, add an entity shape and a relationship shape, and group the two shapes together. An associative entity (easier to see in the second type of diagram), is shown with a dashed outline and connector – this type of entity is needed wherever you have many-to-many relationships.A weak entity (shown as a double rectangle), because it doesn’t have it’s own unique key – it only exists in relation to entity to which it belongs.Using the HabitTracker example that I have used in previous posts, the entities are: User, Coach, Habit, Checkin, and Comment. A second entity following this example would be Course, which would include the attributes Professor, a list of enrolled Students, and the Subjects that the Course contains. These represent a collection of data, using a rectangle with attributes ‘hanging’ off it, or box containing a list of its attributes.įor example, an entity Student could include the attributes StudentID, Name, Address, Course, Subjects, Marks.
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