Make sure you keep a good backup copy before proceeding with the amendments to your database.

Also you can consider using a plugin to allow access to modify your db. Like this: WP-DBManager by Lester Chan.

Be aware – you may need to change the name of the db tables for these commands to work on your dbs.

Here is the command to run to remove all post revisions:

DELETE FROM wp_posts WHERE post_status = “revision”

To remove annoyoing inherit posts that may have crept inb there:

DELETE FROM wp_posts WHERE post_status = “inherit”