WordPress stores a record called revision of each saved draft or published update. This system allows you to see what changes were made in each post and page over time. However, as you use WordPress, this can lead to a lot of unnecessary overhead in your WordPress database, which consumes a lot of space and make your site sluggish and bloated.
You can either use our plugin Advanced Database Cleaner to clean-up these revisions or execute the following SQL code (which is used by the plugin) directly via your phpMyAdmin:
DELETE FROM posts WHERE post_type = 'revision'