# 1709. Biggest Window Between Visits

<https://leetcode.com/problems/biggest-window-between-visits>

## Description

Table: `UserVisits`

```
+-------------+------+
| Column Name | Type |
+-------------+------+
| user\_id     | int  |
| visit\_date  | date |
+-------------+------+
This table does not have a primary key.
This table contains logs of the dates that users vistied a certain retailer.
```

Assume today's date is `'2021-1-1'`.

Write an SQL query that will, for each `user_id`, find out the largest `window` of days between each visit and the one right after it (or today if you are considering the last visit).

Return the result table ordered by `user_id`.

The query result format is in the following example:

```
UserVisits table:
+---------+------------+
| user\_id | visit\_date |
+---------+------------+
| 1       | 2020-11-28 |
| 1       | 2020-10-20 |
| 1       | 2020-12-3  |
| 2       | 2020-10-5  |
| 2       | 2020-12-9  |
| 3       | 2020-11-11 |
+---------+------------+
Result table:
+---------+---------------+
| user\_id | biggest\_window|
+---------+---------------+
| 1       | 39            |
| 2       | 65            |
| 3       | 51            |
+---------+---------------+
For the first user, the windows in question are between dates:
    - 2020-10-20 and 2020-11-28 with a total of 39 days. 
    - 2020-11-28 and 2020-12-3 with a total of 5 days. 
    - 2020-12-3 and 2021-1-1 with a total of 29 days.
Making the biggest window the one with 39 days.
For the second user, the windows in question are between dates:
    - 2020-10-5 and 2020-12-9 with a total of 65 days.
    - 2020-12-9 and 2021-1-1 with a total of 23 days.
Making the biggest window the one with 65 days.
For the third user, the only window in question is between dates 2020-11-11 and 2021-1-1 with a total of 51 days.
```

## ac

```java
```