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I am reading the book Database Processing, 14th Edition. In chapter 5, Min and Max Cardinality are discussed. My question is mainly focused on min cardinality. For example, it is mentioned that a department has one or more employees while employee belongs to 0 or more department. The figure is as follows:

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I have drawn the following diagram to understand how to place the oval and vertical bar for min, and the N and 1 for max cardinality

enter image description here

It seems to me both min and max cardinalities are reversed in the figure provided by the book. If an employee may not belong to a department, why oval is placed next to department? Similar question goes for max cardinality

I would deeply appreciate if someone could help me understand and further recommend detailed tutorials as the explanation in the book is not sufficient for me to understand. Note that I have read other tutorials, book, etc that use different notations, but I need to learn the notation from the above book.

Melanie A
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  • There are multiple ways of drawing cardinalities in diagrams. Your book's drawing doesn't seem to follow any particular standard: looks like a cross between Chen and Crow's Foot. I tend to prefer the "Crow's Foot" notation, but that's just me. See https://en.wikipedia.org/wiki/Entity–relationship_model#Cardinalities – The Impaler Apr 04 '21 at 04:23
  • Thanks for your comments. Unfortunately, I do not have a choice of different notations, and I need to learn and apply the above notation only. – Melanie A Apr 04 '21 at 05:44

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