How to track which users viewed a particular topic?

[mcwumbly (Dave McClure)]

It looks like that post you linked to has an example, in fact:

@ditatompel

Who (logged in user) view specific topic

-- [params]
-- int :topic_id = 1

SELECT
    title,
    viewed_at,
    tv.user_id
FROM topics t
LEFT JOIN topic_views tv
    ON t.id = tv.topic_id
WHERE category_id IS NOT NULL
    AND tv.user_id IS NOT NULL
    AND t.id = :topic_id
ORDER BY viewed_at DESC
LIMIT 1000