Ability to clear watch history of items no longer on server

if i can jump in here…

i have a similar problem in my music library (see my post here: How can i purge missing items from my library? )

i think ‘big wheel’ has helped me fix the problem that caused me to get duplicate entries in the first place, but i still have numerous album thumbnails in my library which point to directories which no longer exist.

can you give me a command or a few that would get rid of any album thumbnails showing in my library which are pointing to non-existant folders?

…and not to be a complete idiot, but where do i get a command line to enter the SQL commands?