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How would you prove that an Entity Relationship Diagram (ERD) was in Third Normal Form (3NF)?

Posted by Guy Beauchamp

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Categories: Domain Modeling, Data Analysis & Modeling


Third normal form of an ER Diagram (ERD) boils down to every attribute depends on the whole primary key of the entity. Inspect the data model to verify

1. every entity has a business primary key (i.e. a key meaningful to the business, not to the database designers!).

2. no attribute in an entity will vary if the value of another attribute is changed (note: the primary key can not be updated once created).

3. no attributes could ever have null values.

4. there are no repeating groups of attributes in the entity.

There is a data modeler’s joke that you can use to lighten the interview (but not recommended for real world parties!): normalization was (in part) created by Ted Codd - a model is in 3NF when every attribute depends on the primary key, the whole key and nothing but the key - so help me Codd!



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Do your homework prior to the business analysis interview!

Having an idea of the type of questions you might be asked during a business analyst interview will not only give you confidence but it will also help you to formulate your thoughts and to be better prepared to answer the interview questions you might get during the interview for a business analyst position.  Of course, just memorizing a list of business analyst interview questions will not make you a great business analyst but it might just help you get that next job.



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