It looks like it was a string named NULL posing as a null value.
I got 0 for ISNULL(suffix), which I assume means false. I tried this
command ...
update persons set suffix = 'Empty' where suffix = '';
It changed the NULLs to Empty.
On Mon, 2007-04-30 at 18:12 -0700, Jeremy Cole wrote:
> Hi John,
>
> Are you sure they are actually NULL and not "NULL" (i.e. the string "NULL")?
>
> Try this:
>
> SELECT first, last, ISNULL(suffix), LENGTH(suffix) FROM persons LIMIT 5;
>
> Regards,
>
> Jeremy
>
> John Kebbel wrote:
> > I'm having problems understanding NULL. I grasp what a NULL value is,
> > but I can't get NULL to perform correctly. For instance, if I do a
> > Select statement, I see that I have columns with a NULL value.
> >
> > select first, last, suffix from persons LIMIT 5;
> > +-----------+----------+--------+
> > | first | last | suffix |
> > +-----------+----------+--------+
> > | Benjamin | Page | NULL |
> > | Jonathan | Watson | NULL |
> > | Jose | Thorson | NULL |
> > | Alejandro | Nickels | NULL |
> > | Griselda | Richards | NULL |
> > +-----------+----------+--------+
> > 5 rows in set (0.01 sec)
> >
> > Logically, it seems that a Select statement should find these five plus
> > any other NULL values in the suffix column. However, such a select
> > statment returns an empty set.
> >
> > mysql> select first, last, suffix from persons where suffix IS NULL;
> > Empty set (0.00 sec)
> >
> > Does anyone see what I'm doing wrong? (Thanks in advance for any help.)
> >
> >
> >
> >
>
