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From:John Kebbel Date:May 1 2007 9:21pm
Subject:Re: IS NULL Question
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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.)
> > 
> > 
> > 
> > 
> 

Thread
IS NULL QuestionJohn Kebbel1 May
  • Re: IS NULL QuestionJeremy Cole1 May
    • Re: IS NULL QuestionJohn Kebbel1 May
  • Re: IS NULL QuestionMartijn Tonies1 May
    • Re: IS NULL QuestionLucas.CTR.Heuman1 May
  • Re: IS NULL QuestionKevin Hunter1 May
    • Re: IS NULL QuestionGerald L. Clark1 May
      • Re: IS NULL QuestionKevin Hunter1 May
    • RE: IS NULL QuestionJerry Schwartz1 May
      • Re: IS NULL QuestionBaron Schwartz1 May
    • batch modeCharles Brown2 May
      • Re: batch modeMogens Melander2 May
        • Re: batch modeMogens Melander2 May