> From: Dan Buettner [mailto:[EMAIL PROTECTED]
> This is a feature - a NULL value is an undefined value,
> therefore two NULL values are not the same. Can be a little
> confusing but makes sense when you think about it.
>
> A UNIQUE index does ensure that non-NULL values are unique;
> you co
> I have an InnoDB table similar to this:
>
> CREATE TABLE Target
> (IMSI VARCHAR(15) ASCII,
> IMEI VARCHAR(15) ASCII,
> UNIQUE KEY (IMSI, IMEI));
>
> After playing a bit with it, I managed to add duplicate records, if one of
> the fields was a NULL:
>
> +-+-+
> |
This is a feature - a NULL value is an undefined value, therefore two
NULL values are not the same. Can be a little confusing but makes
sense when you think about it.
A UNIQUE index does ensure that non-NULL values are unique; you could
specify that your column not accept NULL values.
Dan
On
It is expected behavior, you can make the unique key a primary key
instead. This should prevent this situation.
Ed
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Monday, December 11, 2006 7:42 AM
To: mysql@lists.mysql.com
Subject: UNIQUE KEY vs NULLs
Hi,
I
Hi,
I have an InnoDB table similar to this:
CREATE TABLE Target
(IMSI VARCHAR(15) ASCII,
IMEI VARCHAR(15) ASCII,
UNIQUE KEY (IMSI, IMEI));
After playing a bit with it, I managed to add duplicate records, if one of
the fields was a NULL:
+-+-+
| IMSI
