Default Value Storage

Question

I have the following three tables:

• Item
• Code
• ItemCode (many to many relationship between Item and Code)

And then I have the following sample data on the third table:

Item | Code
-----+-----
001  | A
002  | A
003  | B

There's a possibility that a new Item is added but does not have a code yet. I will assign a default code for this Item, say "Z".

My question is, which is better:

• adding an entry in the ItemCode table every time a new Item is created (with the code value to "Z")

OR

• retrieve the default value from configuration file (and keep the ItemCode table clean from default value entries)

Additional consideration: the default code will always be returned, regardless whether an Item have been assigned a Code or not. So the result from the above data would be:

Code A: Item 001, Item 002
Code B: Item 003
Code Z: Item 001, Item 002, Item 003

Answer 1

Either: don't put a row in ItemCode yet until you know the code (read from file)

Or: make the Code column nullable in ItemCode so it's Unknown/Undefined (depending on your pedantry) and left join/isnull.

I personally don't like storing "default" or "placeholder" values. If you don't know the code, then put nothing. What if you have 2 new items for example?

The other question is: can you deal with this in the client?