From: Krishna Chandra Prajapati (prajapatikcgmail.com)
Date: Wed Oct 13 2010 - 09:46:21 CDT

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Hi Neil,

Yes, primary key is always unique.

In your case, you are using composite key (players_id,default_teams_id).

_Krishna

On Wed, Oct 13, 2010 at 8:07 PM, Tompkins Neil <neil.tompkinsgooglemail.com
> wrote:

> I've the following table. But why isn't the primary key unique, e.g.
> preventing duplicates if entered ?
>
> CREATE TABLE `players_master` (
>
> `players_id` bigint(20) NOT NULL AUTO_INCREMENT,
> `default_teams_id` bigint(20) NOT NULL,
> `first_name` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
> `second_name` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
> `known_as` varchar(200) COLLATE utf8_unicode_ci DEFAULT NULL,
> `dob` date NOT NULL,
> `countries_id` char(2) COLLATE utf8_unicode_ci NOT NULL,
> `retirement_date` date DEFAULT NULL,
> `positions_id` varchar(3) COLLATE utf8_unicode_ci NOT NULL,
> `estimated_value` double NOT NULL DEFAULT '0',
> `contract_wage` double NOT NULL DEFAULT '0',
> `rating` int(11) NOT NULL,
> PRIMARY KEY (`players_id`,`default_teams_id`),
> KEY `FK_players_master_countries_id` (`countries_id`),
> KEY `FK_players_master_positions_id` (`positions_id`),
> KEY `IDX_first_name` (`first_name`),
> KEY `IDX_known_as` (`known_as`),
> KEY `IDX_second_name` (`second_name`),
> KEY `IDX_dob` (`dob`),
> KEY `IDX_estimated_value` (`estimated_value`),
> KEY `IDX_contract_wage` (`contract_wage`),
> KEY `IDX_rating` (`rating`),
> KEY `FK_players_master_teams_id` (`default_teams_id`),
> CONSTRAINT `FK_players_master_countries_id` FOREIGN KEY (`countries_id`)
> REFERENCES `countries` (`countries_id`) ON DELETE NO ACTION ON UPDATE NO
> ACTION,
> CONSTRAINT `FK_players_master_positions_id` FOREIGN KEY (`positions_id`)
> REFERENCES `positions` (`positions_id`) ON DELETE NO ACTION ON UPDATE NO
> ACTION,
> CONSTRAINT `FK_players_master_teams_id` FOREIGN KEY (`default_teams_id`)
> REFERENCES `teams_master` (`teams_id`) ON DELETE NO ACTION ON UPDATE NO
> ACTION
> ) ENGINE=InnoDB AUTO_INCREMENT=1001 DEFAULT CHARSET=utf8
> COLLATE=utf8_unicode_ci
>
> I'm confused, I thought primary keys were always unique ?
>
> Cheers
> Neil
>

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]