Entity Relationship Diagram. How does the IS A relationship translate into tables?

Question

I was simply wondering, how an ISA relationship in an ER diagram would transl

Answer 1

It depends entirely on the nature of the relationships.

IF the relationship between a Person and a Student is 1 to N (one to many), then the correct way would be to create a foreign key relationship, where the Student has a foreign key back to the Person's ID Primary Key Column. Same thing for the Person to Teacher relationship.

However, if the relationship is M to N (many to many), then you would want to create a separate table containing those relationships.

Assuming your ERD uses 1 to N relationships, your table structure ought to look something like this:

CREATE TABLE Person ( sin bigint, name text, PRIMARY KEY (sin) );

CREATE TABLE Student ( GPA float, fk_sin bigint, FOREIGN KEY (fk_sin) REFERENCES Person(sin) );

and follow the same example for the Teacher table. This approach will get you to 3rd Normal Form most of the time.