Count Article Types Viewed

You are given article view events and article metadata. `article_views(user_id INT, article_id INT, view_date DATE)` - One row per article view event. `articles(article_id INT, article_type VARCHAR)` - Maps each article to its type. Join key: `article_views.article_id = articles.article_id`. Assume `view_date` is a calendar date and timezone handling is not needed. Tasks: 1. For `2019-01-01`, return the number of distinct article types viewed by each user. 2. Build a histogram of the number of distinct article types viewed per user across the full dataset. In other words, for each possible `num_article_types`, return how many users viewed exactly that many distinct article types. Definitions: - If a user views multiple articles of the same `article_type`, count that type only once for that user. - For the histogram in task 2, use all available dates unless otherwise stated. Required output: - Task 1: `user_id, num_article_types` - Task 2: `num_article_types, num_users`