|Subject||Re: [firebird-support] Why NULL <> NULL ?|
>>>Often used example:etc
>>>I don't know how much money you've got in your wallet, so the value is
>>>You don't know how much money I've got in my wallet, so it's NULL, too.
>> I've never thought of this as a good example.
>> I have money in my wallet - it could be nothing or it could be $5 or $10
>> In the DB, if the field state is NULL - it NEVER has an unknown value init
>> of 5 or 10 - it has no value it's state is NULL. if it has 5 or 10 in itNot always, remember the mantra? "null is a state, not a value".
>> then it is NOT NULL.
>But the key here is that NULL means unknown (to others than the wallet
state <> unknown.
We can know the state: it's either NULL or NOT NULL.
>owner in the above example). So, to the wallet owner, the amount of:-)
>money in his/her wallet is NOT NULL (unless he/she hasn't counted it for
>a while...), but to the rest of the world, it's NULL.
Oh, thy lovely NULL.
Database Workbench - development tool for Firebird and more!
Database development questions? Check the forum!