From: Martijn Tonies
Date: October 3 2005 10:29am
Subject: Re: Double indexes on one field
List-Archive: http://lists.mysql.com/mysql/189850
Message-Id: <01fd01c5c805$512c5a20$c802a8c0@martijnws>
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> Using PhpMyAdmin, I seldom get the warning message:
> PRIMARY and INDEX keys should not both be set for column `ID`
>
> I understand its meaning, but I was wondering to what extent having a
> field indexed AND being a primary key might slow down/speed up my
> queries.
>
> Is that gonna take twice the time if I am searching on the ID field,
> just because there are two indexes?
>
> I'd like to have a rough idea of how serioulsy I need to avoid these.

Creating a PRIMARY KEY will automatically create an index.

Why would you create a second index for that field?

With regards,

Martijn Tonies
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