Is it bad to use redundant relationships?

Question

Suppose I have the following tables in my database:

Now all my queries depend on Company table. Is it a bad practice to give every other table a (redundant) relationships to the Company table to simplify my sql queries?

Edit 1: Background is a usage problem with a framework. See Django: limiting model data.

Edit 2: No tuple would change his company.

Edit 3: I don't write the mysql queries. I use a abstraction layer (django).

Answer 1

It is bad practice because your redundant data has to be updated independently and therefore redundantly. A process that is fraught with potential for error. (Even automatic cascading has to be assigned and maintained separately)

By introducing this relation you effectively denormalize your database. Denormalization is sometimes necessary for the sake of performance but from your question it sounds like you're just simplifying your SQL.

Use other mechanisms to abstract the complexity of your database: Views, Stored Procs, UDFs

Answer 2

What you are asking is whether to violate Third Normal Form in your design. Doing so is not something to be done without good reason because by creating redundancy you create the possibility for errors and inconsistencies in your data. Also, "simplifying" the model with redundant data to support some operations is likely to complicate other operations. Also, constraints and other data access logic will likely need to be duplicated unnecessarily.