Question

1149. Article Views II

中文文档

Description

Table: Views

+---------------+---------+
| Column Name   | Type  |
+---------------+---------+
| article_id  | int   |
| author_id   | int   |
| viewer_id   | int   |
| view_date   | date  |
+---------------+---------+
This table may have duplicate rows.
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.

 

Write a solution to find all the people who viewed more than one article on the same date.

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 |
| 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 |
+------------+-----------+-----------+------------+
Output: 
+------+
| id   |
+------+
| 5  |
| 6  |
+------+

Solutions

Solution 1

# Write your MySQL query statement below
SELECT DISTINCT viewer_id AS id
FROM Views
GROUP BY viewer_id, view_date
HAVING COUNT(DISTINCT article_id) > 1
ORDER BY 1;