Skip to content

Latest commit

 

History

History
73 lines (58 loc) · 1.96 KB

File metadata and controls

73 lines (58 loc) · 1.96 KB

中文文档

Description

Table: Views

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| article_id    | int     |
| author_id     | int     |
| viewer_id     | int     |
| view_date     | date    |
+---------------+---------+
There is no primary key for this table, it 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 an SQL query 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 query 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

SQL

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