| article_id | author_id | viewer_id | view_date | | ---------- | --------- | --------- | ---------- | | 1 | 3 | 5 | 2019-08-01 | | 3 | 4 | 5 | 2019-08-01 | | 1 | 3 | 6 | 2019-08-02 | | 2 | 7 | 7 | 2019-08-01 | | 2 | 7 | 6 | 2019-08-02 | | 4 | 7 | 1 | 2019-07-22 | | 3 | 4 | 4 | 2019-07-21 | | 3 | 4 | 4 | 2019-07-21 |