Is there any flag I can set on the column or key to not allow duplicate nulls?
Tim Gustafson MEI Technology Consulting, Inc [EMAIL PROTECTED] (516) 379-0001 Office (516) 480-1870 Mobile/Emergencies (516) 908-4185 Fax http://www.meitech.com/ -----Original Message----- From: Paul DuBois [mailto:[EMAIL PROTECTED] Sent: Tuesday, February 22, 2005 3:13 PM To: Gustafson, Tim; mysql@lists.mysql.com Subject: Re: UNIQUE Key Allowing Duplicate NULL Values At 15:00 -0500 2/22/05, Gustafson, Tim wrote: >Hi there! > >I have a table, defined as follows: > >CREATE TABLE `WebSiteDomainNames` ( > `ID` int(10) unsigned NOT NULL auto_increment, > `WebSite` int(10) unsigned NOT NULL default '0', > `DomainName` int(10) unsigned NOT NULL default '0', > `Alias` char(16) default NULL, > PRIMARY KEY (`ID`), > UNIQUE KEY `DomainName` (`DomainName`,`Alias`), >) ENGINE=InnoDB DEFAULT CHARSET=latin1 > >The way I read this definition, it should be impossible for someone to >put in two rows with the same DomainName and Alias, however, right now I >have the following rows in the table: > >+-----+---------+------------+-------+ >| ID | WebSite | DomainName | Alias | >+-----+---------+------------+-------+ >| 543 | 1086 | 1334 | NULL | >| 545 | 1086 | 1334 | NULL | >| 509 | 1086 | 1334 | * | >+-----+---------+------------+-------+ > >And I can insert even more NULL rows if I want to. Shouldn't the UNIQUE >key prevent this from happening? Not for NULL values, no. See the description for UNIQUE indexes here: http://dev.mysql.com/doc/mysql/en/create-table.html -- Paul DuBois, MySQL Documentation Team Madison, Wisconsin, USA MySQL AB, www.mysql.com
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