there is a blog post tagged with 'analytics' and 'advanced sql' which i believe has an error, but i cannot find a way to leave a commet (searching within the community does not return the post, perhaps because it dates back to 2014?) the blog post is here.

the error, i believe, is in the first code snippet under 'reactivated users' (the third section). the group by clause is 'group by 2'. i believe it should be 'group by 1' as the former returns an sql error.