Table: Views
+---------------+---------+ | Column Name | Type | +---------------+---------+ | article_id | int | | author_id | int | | viewer_id | int | | view_date | date | +---------------+---------+ The table may have duplicate rows (In other words, there is no primary key for this table in SQL). Each row of this table indicates that some viewer viewed an article (written by some author) on some date. Note that equal author_id and viewer_id indicate the same person.
Find all the authors that viewed at least one of their own articles.
Return the result table sorted by id in ascending order.
The result format is in the following example.
Example 1:
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 | +------+
# Write your MySQL query statement below
SELECT DISTINCT author_id AS id
FROM Views
WHERE author_id = viewer_id
ORDER BY 1;