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.)
>
>
>
>
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