If you have been using WordPress for a while, then you should think absolutely about a clean up. Indeed, your database may be full of garbage that make your site sluggish and bloated, such as: revisions, drafts, spam comments, orphan options, orphan tables, etc. You should clean this unnecessary data to reduce the size of your database and improve efficiency when accessing tables. In addition, your backup files will be quicker and smaller.
Advanced Database Cleaner is a must-have plugin that cleans and optimizes your WordPress database (you can download thefree versionfrom wordpress.org).