Now that WordPress has been updated there is a much simpler way to delete approved comments in bulk.
1. Go to phpmyadmin
2. Choose your database from the left: wrdp1 for example.
3. You will see wp_comments in the main page.
4. Follow that along and select empty.
All comments will now be gone.
Wow its a simple way and very easy to do this.
cjbmeb14 is a superman for this types of problem. thank you much.
