How to display sum of column values ​​from a table?

Question

Ruby on Rails

Hello.
Let's say we have the following scheme:
users (has_many posts)
posts(belongs_to users)
---pages (let's say)
We need to display in the statistics how many pages a particular user has in all his posts. How to implement?

Answer 1

User.find(params[:user_id]).posts.sum(:pages)

Answer 2

pages это что? Если количество страниц для поста, то:
Post.where(user_id: params[:user_id]).sum(:pages)