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1126. Active Businesses

Description

Table: Events

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| business_id   | int     |
| event_type    | varchar |
| occurences    | int     | 
+---------------+---------+
(business_id, event_type) is the primary key (combination of columns with unique values) of this table.
Each row in the table logs the info that an event of some type occurred at some business for a number of times.

 

The average activity for a particular event_type is the average occurences across all companies that have this event.

An active business is a business that has more than one event_type such that their occurences is strictly greater than the average activity for that event.

Write a solution to find all active businesses.

Return the result table in any order.

The result format is in the following example.

 

Example 1:

Input: 
Events table:
+-------------+------------+------------+
| business_id | event_type | occurences |
+-------------+------------+------------+
| 1           | reviews    | 7          |
| 3           | reviews    | 3          |
| 1           | ads        | 11         |
| 2           | ads        | 7          |
| 3           | ads        | 6          |
| 1           | page views | 3          |
| 2           | page views | 12         |
+-------------+------------+------------+
Output: 
+-------------+
| business_id |
+-------------+
| 1           |
+-------------+
Explanation:  
The average activity for each event can be calculated as follows:
- 'reviews': (7+3)/2 = 5
- 'ads': (11+7+6)/3 = 8
- 'page views': (3+12)/2 = 7.5
The business with id=1 has 7 'reviews' events (more than 5) and 11 'ads' events (more than 8), so it is an active business.

Solutions

  • # Write your MySQL query statement below
SELECT business_id
FROM
    EVENTS AS t1
    JOIN (
        SELECT
            event_type,
            AVG(occurences) AS occurences
        FROM EVENTS
        GROUP BY event_type
    ) AS t2
        ON t1.event_type = t2.event_type
WHERE t1.occurences > t2.occurences
GROUP BY business_id
HAVING COUNT(1) > 1;

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