Even if server space is not expensive, it pays to massage the MySQL database back-end of WordPress from time to time.
One example of this is deleting entries for spam comments.
The WordPress blogging system relies on the free MySQL database, which stores the information needed to link all posts to images and themes. Images are stored separately in a folder called ‘uploads’:
< root >/wp-content/uploads, where
< root > is the directory path on the server to the WordPress installation.
The database stores all words typed or copy-pasted into WordPress, including all comments.