l forum but rather to a
general SQL discussion
so I'll try not to comment on that anymore.
Thanks,
Michael
-Original Message-
From: [EMAIL PROTECTED]
To: mysql@lists.mysql.com
Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]
Sent: Thu, 16 Nov 2006 2:55 PM
Subject: Re: finding NULL r
To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; mysql@lists.mysql.com
Sent: Wed, 15 Nov 2006 3:04 PM
Subject: RE: finding NULL records
The result of all but two expressions will be NULL (not 0 or 1) if
either
side is NULL. The two exceptions are the operators IS NULL and IS NOT
NULL.
SELECT NULL
Hi all,
I have to follow-up to myself, as I forgot one important thing:
Joerg Bruehe wrote:
[[...]]
so in SQL for *any* comparison operator "op" ( = < > <> ... LIKE ... )
and *any* known (= non-NULL) value x (column, literal, expression, ...)
the result of
x op NULL
is UNKNOWN.
Th
@lists.mysql.com
Subject: Re: finding NULL records
[[...]]
This is what happens when one of the most innovative concepts of SQL
gets overlooked
or understressed which it seems to be in most modern SQL books.
The thing is that SQL's logic isn't binary. Rather it's built over
three valu
CTED]; mysql@lists.mysql.com
> Subject: Re: finding NULL records
>
> trying to revive an old thread for fun...
>
> > I inherited a system in which the code was writing the
> string "NULL"
> into
> a
> > CHAR field.
>
> This is what happens when one of the most in
trying to revive an old thread for fun...
I inherited a system in which the code was writing the string "NULL"
into
a
CHAR field.
This is what happens when one of the most innovative concepts of SQL
gets overlooked
or understressed which it seems to be in most modern SQL books.
The thing i
> I inherited a system in which the code was writing the string "NULL" into
a
> CHAR field. It took me a long time to figure out what MySQL CLI was
showing
> me.
>
> These kids today...
Oh my, sounds like a candidate for www.thedailywtf.com :-)
Martijn Tonies
Database Workbench - development
I inherited a system in which the code was writing the string "NULL" into a
CHAR field. It took me a long time to figure out what MySQL CLI was showing
me.
These kids today...
Regards,
Jerry Schwartz
Global Information Incorporated
195 Farmington Ave.
Farmington, CT 06032
860.674.8796 / FAX: 86
[snip]
>And the reason for that is because nothing is actually equal to NULL.
>For a field to be equal to NULL it would actually have to contain NULL,
>in which case it would not be actually NULL.
What?
NULL doesn't equal NULL because NULL means "unknown".
A column can have 2 states: known or un
>>> SELECT * FROM tests WHERE test_id IS NULL
>>
>> Yes, that works, but I was also trying SELECT * instead of just the
>key
>> field (just a typo in the example). The problem was in the equal sign
>
>> versus the 'IS' operator. Any reason why MySQL does not honor
>> =NULL? Seems kind of odd.
>Of course this will return an empty set because you have only selected
>the test_id, try this;
>
>SELECT * FROM tests WHERE test_id IS NULL
Empty set <> "empty column"
Martijn Tonies
Database Workbench - tool for InterBase, Firebird, MySQL, NexusDB, Oracle &
MS SQL Server
Upscene Productions
ht
[snip]
Alan Nilsson wrote:
>
> On Oct 30, 2006, at 3:27 PM, Jay Blanchard wrote:
>
>> [snip]
>> I am trying to find records where the value of a filed is NULL. I
>> know that there are records that have null values but the result is
>> always an empty set.
>>
>> eg:
>> select test_id from tests
Alan Nilsson wrote:
On Oct 30, 2006, at 3:27 PM, Jay Blanchard wrote:
[snip]
I am trying to find records where the value of a filed is NULL. I
know that there are records that have null values but the result is
always an empty set.
eg:
select test_id from tests where test_id=NULL
always ret
On Oct 30, 2006, at 3:27 PM, Jay Blanchard wrote:
[snip]
I am trying to find records where the value of a filed is NULL. I
know that there are records that have null values but the result is
always an empty set.
eg:
select test_id from tests where test_id=NULL
always returns an empty set whe
[snip]
I am trying to find records where the value of a filed is NULL. I
know that there are records that have null values but the result is
always an empty set.
eg:
select test_id from tests where test_id=NULL
always returns an empty set when there are in fact records that have
a null val
I am trying to find records where the value of a filed is NULL. I
know that there are records that have null values but the result is
always an empty set.
eg:
select test_id from tests where test_id=NULL
always returns an empty set when there are in fact records that have
a null value for
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