Re: boolean datatype ... wtf?

On 06/10/2010 6:51 AM, Bob Badour wrote:
> Null is an indicator that evaluates to NULL or NOT NULL. ie. it is a
> boolean.

This makes me want to take another stab at an old point. I think it is a boolean and how it's constructed within a relational db seems crucial which I'd say it can't be in any logical way. Maybe this is part of what what Erwin S means too.

It's reminiscent of how Table_Dee has a maximum cardinality of one, whereas a made-up domain such as {'Yes', 'No'} is something else when it is specified by an attribute. To construct NOT Table_Dee, we use a relation that has no tuples, such as Table_Dum, but that's not the same thing as imagining that we can record all the values of some boolean domain in a single relation. I'd say it needs to be more widely understood that it is the empty relation which means 'NOT' where a relational db is concerned. Received on Wed Oct 06 2010 - 17:00:16 CEST