common_schema booth in Percona Live 2013 (someone left their soup on our table)

Allen Kinnard

Yay! I got a booth!

I confess it was mostly deserted. My hero Allen Kinnard, whom I've never met before, was kind enough to volunteer to occupy the booth.
So between him and me, both of course also looking to visit other booths and talk to people, the common_schema booth was only moderately attended.

Well, this was the DotOrg Pavilion: free booths for free & open source projects (e.g.

Introduction

A question I recently saw on Stack Overflow titled Faster way to delete matching [database] rows? prompted me to organize my thoughts and observations on the subject and quickly jot them down here.

Here is the brief description of the task: say, you have 2 MySQL tables a and b. The tables contain the same type of data, for example log entries. Now you want to delete all or a subset of the entries in table a that exist in table b.

Solutions Suggested By Others

DELETE FROM a WHERE EXISTS (SELECT b.id FROM b WHERE b.id = a.id);

DELETE a FROM a INNER JOIN b on a.id=b.id;

DELETE FROM a WHERE id IN (SELECT id FROM b)

The Problem With  [Read more...]