From: Date: April 16 2008 12:30am
Subject: Re: select does too much work to find rows where primary key does not match
List-Archive: http://lists.mysql.com/mysql/212303
Message-Id: <200804152230.m3FMUu3O023318@mx.swagman.com>

> I would have thought your not = though is matching a lot more rows every time..

The field is UNIQUE PRIMARY KEY in both tables, so there
should be 0 or 1 matches.

> I would look into using where not exists as a subselect

My MySQL book (O'Reilly second edition) does not mention
subqueries or EXISTS. I am reading about it online now.

> delete from bar where not exists (select 'y' from foo where foo.phone = bar.phone);
>
> something like that.

Thanks, I'll give it a try.