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2752. Customers with Maximum Number of Transactions on Consecutive Days

Description

Table: Transactions

+------------------+------+
| Column Name      | Type |
+------------------+------+
| transaction_id   | int  |
| customer_id      | int  |
| transaction_date | date |
| amount           | int  |
+------------------+------+
transaction_id is the column with unique values of this table.
Each row contains information about transactions that includes unique (customer_id, transaction_date) along with the corresponding customer_id and amount.   

Write a solution to find all customer_id who made the maximum number of transactions on consecutive days.

Return all customer_id with the maximum number of consecutive transactions. Order the result table by customer_id in ascending order.

The result format is in the following example.

 

Example 1:

Input: 
Transactions table:
+----------------+-------------+------------------+--------+
| transaction_id | customer_id | transaction_date | amount |
+----------------+-------------+------------------+--------+
| 1              | 101         | 2023-05-01       | 100    |
| 2              | 101         | 2023-05-02       | 150    |
| 3              | 101         | 2023-05-03       | 200    |
| 4              | 102         | 2023-05-01       | 50     |
| 5              | 102         | 2023-05-03       | 100    |
| 6              | 102         | 2023-05-04       | 200    |
| 7              | 105         | 2023-05-01       | 100    |
| 8              | 105         | 2023-05-02       | 150    |
| 9              | 105         | 2023-05-03       | 200    |
+----------------+-------------+------------------+--------+
Output: 
+-------------+
| customer_id | 
+-------------+
| 101         | 
| 105         | 
+-------------+
Explanation: 
- customer_id 101 has a total of 3 transactions, and all of them are consecutive.
- customer_id 102 has a total of 3 transactions, but only 2 of them are consecutive. 
- customer_id 105 has a total of 3 transactions, and all of them are consecutive.
In total, the highest number of consecutive transactions is 3, achieved by customer_id 101 and 105. The customer_id are sorted in ascending order.

Solutions

• SQL

• # Write your MySQL query statement below
  WITH
      s AS (
          SELECT
              customer_id,
              DATE_SUB(
                  transaction_date,
                  INTERVAL ROW_NUMBER() OVER (
                      PARTITION BY customer_id
                      ORDER BY transaction_date
                  ) DAY
              ) AS transaction_date
          FROM Transactions
      ),
      t AS (
          SELECT customer_id, transaction_date, COUNT(1) AS cnt
          FROM s
          GROUP BY 1, 2
      )
  SELECT customer_id
  FROM t
  WHERE cnt = (SELECT MAX(cnt) FROM t)
  ORDER BY customer_id;
  
  

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