CODEWITHSUNDEEP
sqldatabase-designrelational-databasedatabase-schemaentity-relationship
Hidoshi
Hidoshi

Reputation: 33

Representing inheritance in an Entity Relational to Relational Mapping diagram

I have an Entity Relational Diagram for a library management system. I have the entities "Member" and "Professor", and "Professor" inherits attributes from "Member".

Then I have my ER to relational mapping diagram and here is the issue I am facing - how to represent the connection between "Member" and "Professor"?enter image description here

enter image description here

Here are the diagrams, as you can see there is no Professor added to the 2nd diagram. Any tips are appreciated.

Upvotes: 1

Views: 539

Answers (1)

reaanb
reaanb

Reputation: 10065

Subtypes normally use the same primary key as the supertype, and record any additional attributes. In your example, Professor has no additional attributes besides the SSN that identifies it as a Member. So, in your relational diagram you would draw a Professors table with a single column - Member_SSN - which points back to the SSN column of Members.

Upvotes: 1

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