Which normal form does this table violate?

Question

Consider this table:

   +-------+-------+-------+-------+  
   | name  |hobby1 |hobby2 |hobby3 |  
   +-------+-------+-------+-------+   
   | kris  | ball           


        

Answer 1

You say that the hobbies belong to the same domain and that they can move around in the columns. If by this you mean that for any specific name the list of hobbies is in an arbitrary order and kriss could just as easily have dance, ball, swim as ball, swim, dance, then I would say you have a repeating group and the table violates 1NF.

If, on the other hand, there is some fundamental semantic difference between a particular person's first and second hobbies, then there may be an argument for saying that the hobbies are not repeating groups and the table may be in 3NF (assuming that hobby columns are FK to a hobby table). I would suggest that this argument, if it exists, is weak.

One other factor to consider is why there are precisely 3 hobbies and whether more or fewer hobbies are a potential concern. This factor is important not so much for normalization as for flexibility of design. This is one reason I would split the hobbies into rows, even if they are semantically different from one-another.