3NF question. One for the smart ppl here.

[Chunk]

I have table with the functional dependencies shown above.

I would like to know if it is in 3rd Normal Form. I think it is.

The table stores data on DVDs and Tapes.

Format = "Tape" or "DVD".

Region is either "1","2","3" or "0" (If format is DVD)
or "PAL" or "NTSC" (If format is Tape).

Rarity is a rating (1 to 5) of how rare a tape or dvd is. The user uses their descretion when deciding this value, but the take format and region into account when deciding.

Price is the cost of the tape or dvd. The rarity, region, and format are considered when the user decides upon a price.

Region, rarity and format are unique, and can only appear once in the table.

Finally, Price band is the primary key of the table. It is a value used solely to identify the combination of Format, region and rarity.

Im not sure if I have done the diagram correctly. Im not sure if I need to model a dependency if it is only there because the user is using data when deciding on the value of other data.

In which case, would this be the correct diagram, and is it in 3NF?

 

[Uncle Gizmo]

>>>> Price band is the primary key of the table. It is a value used solely to identify the combination of Format, region and rarity<<<<<

You can do that (above) but I believe that it is better practice to not have the primary key as a separate field, as in this case, where multiple fields can be indexed to provide a primary key. I am not sure which normal form level this idea applies to though.

As a general rule, if it works, why worry! As your experience and abilities improve, I'm sure you will go back through and redesign your databases to conform more and more to the industry standards.