# 1939. Users That Actively Request Confirmation Messages

https://leetcode.com/problems/users-that-actively-request-confirmation-messages

## Description

Table: `Signups`

```
+----------------+----------+
| Column Name    | Type     |
+----------------+----------+
| user\_id        | int      |
| time\_stamp     | datetime |
+----------------+----------+
user\_id is the primary key for this table.
Each row contains information about the signup time for the user with ID user\_id.
```

Table: `Confirmations`

```
+----------------+----------+
| Column Name    | Type     |
+----------------+----------+
| user\_id        | int      |
| time\_stamp     | datetime |
| action         | ENUM     |
+----------------+----------+
(user\_id, time\_stamp) is the primary key for this table.
user\_id is a foreign key with a reference to the Signups table.
action is an ENUM of the type ('confirmed', 'timeout')
Each row of this table indicates that the user with ID user\_id requested a confirmation message at time\_stamp and that confirmation message was either confirmed ('confirmed') or expired without confirming ('timeout').
```

Write an SQL query to find the IDs of the users that requested a confirmation message **twice** within a 24-hour window. Two messages exactly 24 hours apart are considered to be within the window. The `action` does not affect the answer, only the request time.

Return the result table **in any order**.

The query result format is in the following example:

```
Signups table:
+---------+---------------------+
| user\_id | time\_stamp          |
+---------+---------------------+
| 3       | 2020-03-21 10:16:13 |
| 7       | 2020-01-04 13:57:59 |
| 2       | 2020-07-29 23:09:44 |
| 6       | 2020-12-09 10:39:37 |
+---------+---------------------+
Confirmations table:
+---------+---------------------+-----------+
| user\_id | time\_stamp          | action    |
+---------+---------------------+-----------+
| 3       | 2021-01-06 03:30:46 | timeout   |
| 3       | 2021-01-06 03:37:45 | timeout   |
| 7       | 2021-06-12 11:57:29 | confirmed |
| 7       | 2021-06-13 11:57:30 | confirmed |
| 2       | 2021-01-22 00:00:00 | confirmed |
| 2       | 2021-01-23 00:00:00 | timeout   |
| 6       | 2021-10-23 14:14:14 | confirmed |
| 6       | 2021-10-24 14:14:13 | timeout   |
+---------+---------------------+-----------+
Result table
+---------+
| user\_id |
+---------+
| 2       |
| 3       |
| 6       |
+---------+
User 2 requested two messages within exactly 24 hours of each other, so we include them.
User 3 requested two messages within 6 minutes and 59 seconds of each other, so we include them.
User 6 requested two messages within 23 hours, 59 minutes, and 59 seconds of each other, so we include them.
User 7 requested two messages within 24 hours and 1 second of each other, so we exclude them from the answer.
```

## ac

```java
```
