freakable on "How to change this sql querry"

# First:

DELETE FROM wp_postmeta
WHERE post_id IN
(
SELECT id
FROM wp_posts
WHERE post_type = 'attachment'
)
;

# Second:

DELETE FROM wp_posts WHERE post_type = 'attachment'

That sql querry delete every attachment from post. I need to change this, to delete every attachment with height less than 100px. Can someone help me ?