"Jeff Gardner" wrote...
> Jeff Gardner wrote:
>> Radoulov, Dimitre wrote:
>>> "Jeff Gardner" wrote...
>>>> Greetings:
>>>>
>>>> I am trying to locate incorrect data in a column using REGEXP. Only
>>>> numeric data is allowed but I am importing data, some of which is not
>>>> properly formatted. I am using:
>>>>
>>>> SELECT *
>>>> FROM `table`
>>>> WHERE `column` REGEXP "[^[:digit:]]";
>>>>
>>>> to locate any value that is not a number. I've tried several
>>>> variations and I get an empty set back. I know that there are illegal
>>>> characters in some of the data but I can't seem to locate it using this
>>>> query. The field can contain anywhere from 1 to 6 digits, if that is
>>>> relevant. Advice is much appreciated.
[...]
> It turns out that there were 13 rows with a NULL value in the field in
> question. NULL is not whitespace, nor is it digits. Any explanation as
> to why the above query returned no rows?

Because of its special meaning, I suppose.

"Conceptually, NULL means "a missing unknown value" and it is treated
somewhat differently from other values. "

Unknown means that you cannot _know_ whether it's a digit or something else
(btw, whitespaces are handled correctly with your example query).

So,
a) Use constraints (not null)
or
b) Add "column is not null" in your query


Regards
Dimitre