LeetCode in Kotlin
1890. The Latest Login in 2020
Easy
SQL Schema
Table: Logins
+----------------+----------+
| Column Name | Type |
+----------------+----------+
| user_id | int |
| time_stamp | datetime |
+----------------+----------+
(user_id, time_stamp) is the primary key for this table.
Each row contains information about the login time for the user with ID user_id.
Write an SQL query to report the latest login for all users in the year 2020. Do not include the users who did not login in 2020.
Return the result table in any order.
The query result format is in the following example.
Example 1:
Input:
Logins table:
+---------+---------------------+
| user_id | time_stamp |
+---------+---------------------+
| 6 | 2020-06-30 15:06:07 |
| 6 | 2021-04-21 14:06:06 |
| 6 | 2019-03-07 00:18:15 |
| 8 | 2020-02-01 05:10:53 |
| 8 | 2020-12-30 00:46:50 |
| 2 | 2020-01-16 02:49:50 |
| 2 | 2019-08-25 07:59:08 |
| 14 | 2019-07-14 09:00:00 |
| 14 | 2021-01-06 11:59:59 |
+---------+---------------------+
Output:
+---------+---------------------+
| user_id | last_stamp |
+---------+---------------------+
| 6 | 2020-06-30 15:06:07 |
| 8 | 2020-12-30 00:46:50 |
| 2 | 2020-01-16 02:49:50 |
+---------+---------------------+
Explanation:
User 6 logged into their account 3 times but only once in 2020, so we include this login in the result table.
User 8 logged into their account 2 times in 2020, once in February and once in December. We include only the latest one (December) in the result table.
User 2 logged into their account 2 times but only once in 2020, so we include this login in the result table.
User 14 did not login in 2020, so we do not include them in the result table.
Solution
# Write your MySQL query statement below
SELECT user_id, MAX(time_stamp) AS last_stamp
FROM Logins
WHERE YEAR(time_stamp) = '2020'
GROUP BY 1;