Article Views I

Task: Find all the authors that viewed at least one of their own articles. Return the result table sorted by id in ascending order.

Table: Views

+-------------+------+
| Column Name | Type |
+-------------+------+
| article_id  | INT  |
| author_id   | INT  |
| viewer_id   | INT  |
| view_date   | date |
+-------------+------+

Input: Views table:

+------------+-----------+-----------+------------+
| article_id | author_id | viewer_id | view_date  |
+------------+-----------+-----------+------------+
| 1          | 3         | 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 |
+------------+-----------+-----------+------------+

Output:

+----+
| id |
+----+
| 4  |
| 7  |
+----+