Comments on: No business value in nulls http://robertlambert.net/2009/04/no-business-value-in-nulls/ on business-aligned information technology Wed, 01 Sep 2010 14:35:28 +0000 hourly 1 http://wordpress.org/?v=3.0.1 By: Bob http://robertlambert.net/2009/04/no-business-value-in-nulls/comment-page-1/#comment-51 Bob Wed, 08 Apr 2009 18:07:46 +0000 http://robertlambert.net/?p=345#comment-51 Andy, great examples, and I definitely agree with your approach. Still, it seems to me they are about how to represent the business requirement in a design. Nulls are a valid tool for the DB/code-literate in design, but in terms of business requirements I still think probably never. I think of all business requirements working on normalized data, thereby giving the designer/developer full control of design decisions and not cutting off any data design options. Given that, to me the player_average table is a (probably appropriate) denormalization of the player_at_bat_event table, of which there would be no row for the player who has not yet faced a pitcher. So I think we're coming from the same place, just in different stages of the development life cycle. I suppose a clarifying comment is in order: "no business value in nulls until design." Andy, great examples, and I definitely agree with your approach. Still, it seems to me they are about how to represent the business requirement in a design. Nulls are a valid tool for the DB/code-literate in design, but in terms of business requirements I still think probably never. I think of all business requirements working on normalized data, thereby giving the designer/developer full control of design decisions and not cutting off any data design options. Given that, to me the player_average table is a (probably appropriate) denormalization of the player_at_bat_event table, of which there would be no row for the player who has not yet faced a pitcher. So I think we’re coming from the same place, just in different stages of the development life cycle. I suppose a clarifying comment is in order: “no business value in nulls until design.”

]]> By: Andy http://robertlambert.net/2009/04/no-business-value-in-nulls/comment-page-1/#comment-50 Andy Tue, 07 Apr 2009 18:46:10 +0000 http://robertlambert.net/?p=345#comment-50 It seems to me that a null might imply a business value, depending on the scenario. In the examples you provided, I'd agree nulls don't make much sense. What if we have a database table tracking a baseball team's players' batting averages? - You might have a value 0.500 for a player who gets on base every other time. - Or 0.000 if a player has never reached first base (no pun intended) - Or null for a player who hasn't been to bat yet? Now, to your point you could probably achieve the same result with an alternate design: perhaps a separate player table from player_average or whatever, such that only players who have been at bat are in the player_average table. But this might not always be the best design, or perhaps not possible due to other design constraints. Similar examples exist in the Java world - do I return a null Collection or a Collection of size 0? I think, like many other problems in the database/software architecture world, what's important is to approach the problem consistently and be sure there's a common understanding across the team. It seems to me that a null might imply a business value, depending on the scenario. In the examples you provided, I’d agree nulls don’t make much sense.

What if we have a database table tracking a baseball team’s players’ batting averages?

- You might have a value 0.500 for a player who gets on base every other time.
- Or 0.000 if a player has never reached first base (no pun intended)
- Or null for a player who hasn’t been to bat yet?

Now, to your point you could probably achieve the same result with an alternate design: perhaps a separate player table from player_average or whatever, such that only players who have been at bat are in the player_average table. But this might not always be the best design, or perhaps not possible due to other design constraints.

Similar examples exist in the Java world – do I return a null Collection or a Collection of size 0? I think, like many other problems in the database/software architecture world, what’s important is to approach the problem consistently and be sure there’s a common understanding across the team.

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