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From:Jerry Schwartz Date:May 1 2007 4:15pm
Subject:RE: IS NULL Question
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We use NULL all the time with MyISAM tables, and I've never noticed a
problem.

Well, there was one bizarre bit of business that's already been mentioned:
my predecessor actually put the string "NULL" into a field, and since it
looks the same in the MySQL client that gave me a devil of a time.

Regards,

Jerry Schwartz
Global Information Incorporated
195 Farmington Ave.
Farmington, CT 06032

860.674.8796 / FAX: 860.674.8341


> -----Original Message-----
> From: Kevin Hunter [mailto:hunteke@stripped]
> Sent: Tuesday, May 01, 2007 11:37 AM
> To: John Kebbel
> Cc: MySQL List
> Subject: Re: IS NULL Question
>
> At 9:06p -0400 on 30 Apr 2007 John Kebbel wrote:
> > I'm having problems understanding NULL. I grasp what a NULL
> value is,
>
> A NULL value is rather an oxymoron.  It'd be more accurate to say
> that NULL means "absence of a value".
>
> > 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.)
>
> Caveat emptor: I haven't tested this in about a year.
>
> Are you perchance using a table type of MyISAM?  I seem to recall
> that MyISAM has a hard time actually representing NULL internally.
> [ ... Thinks for a minute ... ]  I remember something about spaces,
> like, I think I did
>
> INSERT ( val1, val2, NULL ) INTO myTable;
>
> and was only able to get the tuples back when I did
>
> SELECT * FROM myTable WHERE col3 = ' ';  -- a space character
>
> If this is the case, you might consider using a different
> table type,
> such as InnoDB.
>
> HTH,
>
> Kevin
>
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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