When i was googling i find a good and simple WordPress plugin, Optimize DB. This plugin created and owned by Yoast.com. I try this plugin and i think it’s a good plugin. You don’t use any hard code and you don’t need make any change your WordPress system. Just upload and activate.

After you activate this plugin, go to Tools > Optimize DB and you get a report about your DB. And click to Optimize Now! That’s All!

Plugins Page:

Optimize DB – Yoast