Table Posts:
id body
1  test1

Table user_views
post_id user_id
1       1

select count(uv.post_id) as views_count,posts.id,posts.body from posts
left join user_views uv on uv.post_id = posts.id
group by posts.id

select count(*) from posts where posts.id not in select post_id from user_views where post_id = posts.id and user_id = 1