# 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

• # 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;