Table: Purchases
+---------------+------+ | Column Name | Type | +---------------+------+ | purchase_id | int | | user_id | int | | purchase_date | date | +---------------+------+ purchase_id is the primary key for this table. This table contains logs of the dates that users purchased from a certain retailer.
Write an SQL query to report the IDs of the users that made any two purchases at most 7 days apart.
Return the result table ordered by user_id.
The query result format is in the following example.
Example 1:
Input: Purchases table: +-------------+---------+---------------+ | purchase_id | user_id | purchase_date | +-------------+---------+---------------+ | 4 | 2 | 2022-03-13 | | 1 | 5 | 2022-02-11 | | 3 | 7 | 2022-06-19 | | 6 | 2 | 2022-03-20 | | 5 | 7 | 2022-06-19 | | 2 | 2 | 2022-06-08 | +-------------+---------+---------------+ Output: +---------+ | user_id | +---------+ | 2 | | 7 | +---------+ Explanation: User 2 had two purchases on 2022-03-13 and 2022-03-20. Since the second purchase is within 7 days of the first purchase, we add their ID. User 5 had only 1 purchase. User 7 had two purchases on the same day so we add their ID.