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I'm currently drawing an EER diagram and stumbled across this problem:

Let's say I'm modeling a workplace where all employee's uniquely can be identified by their name (ie no employees share the exact same name) and their employee number. Is this a correct way to model it?

enter image description here

I'm not really sure on whether this is an ok design. Does this design say that Name and Emp_nr together form a unique Employee, or does it say that Name and Emp_nr independently from each other can identify my Employee? I've been searching everywhere and couldn't find a single example on where 2 key attributes is used.

Samuel
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1 Answers1

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This only tells that an Employee has two attributes which are bith a combined primary key

  1. he has a name and
  2. a employer number

In a Table structure , it will be displayer as two columns for the Table Employee and the would have a PRIMARY KEY(Emp_nr,Name)

Employee
-------
Emp_nr

Name
nbk
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  • If neither was underlined, they would be regular attributes. I believe underlining an attribute in an EER makes it a key attribute. In this regard, the OP's question appears to be how to make it look that the two attributes are two independent keys instead of their being a single composite key. – Andriy M Oct 19 '20 at 08:03
  • you are right they bit are opart of a combined primary key, i forgot that to mention – nbk Oct 19 '20 at 08:16