Shane Ambler wrote:
> Lutz Steinborn wrote:
>> Jepp, thats it.
>> I've supposed this but can't believe it. So NULL is something out of
>> this
>> dimension :-)
>>
>>
>
> NULL refers to an unknown value - it cannot be said to equal or not
> equal anything other than NULL ...
>
Not exactly. Null does not equal null. The "translation" being does
some-unknown-value equal some-unknown-value? Answer: unknown.
If you want to determine if something is null you must use "is null".
select null = null;
null
select null is null;
true
If you want to treat nulls as a defined known value, use the coalesce
function:
select coalesce(my_column, 'a null value')....;
will return the string 'a null value' whenever my_column is null.
Cheers,
Steve
