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Posted by Steve on 02/06/07 22:27
On Feb 6, 10:25 am, "Paul" <paulwragg2...@hotmail.com> wrote:
> Thanks Plamen, I am just about to go home for the evening so I will
> check this out tommorrow.
>
> I just wanted to post an update before I go home though.
>
> I have been looking a bit more in to this and I have found that the
> following seems even stranger to me.
>
> If I have a column DESCRIPTION VARCHAR(250) and the value is empty
> i.e. NULL then
> shouldn't doing a:
>
> SELECT TAB1.DESCRIPTION
> FROM TABLE1 TAB1
> WHERE TAB1.DESCRIPTION IS NOT NULL
> AND DATALENGTH(TAB1.DESCRIPTION) = 0
>
> always return zero records?
> A VARCHAR is variable length based on the actual data stored in it, so
> shouldn't a VARCHAR column of zero DATALENGTH be NULL?
>
> If anybody can explain this then please do!
>
> I will be looking in to Plamens suggestion tommorrow but in the
> meantime if anybody has any other ideas it will be appreciated!
>
> Thanks,
>
> Paul
An empty string has a DATALENGTH of 0 and is not NULL
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