[LeetCode] 511. Game Play Analysis I

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■ 문제

https://leetcode.com/problems/game-play-analysis-i/

Game Play Analysis I - LeetCode

Table: Activity

+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| player_id    | int     |
| device_id    | int     |
| event_date   | date    |
| games_played | int     |
+--------------+---------+
(player_id, event_date) is the primary key of this table.
This table shows the activity of players of some games.
Each row is a record of a player who logged in and played a number of games (possibly 0) before logging out on someday using some device.

 

Write an SQL query to report the first login date for each player.

Return the result table in any order.

The query result format is in the following example.

 

Example 1:

Input: 
Activity table:
+-----------+-----------+------------+--------------+
| player_id | device_id | event_date | games_played |
+-----------+-----------+------------+--------------+
| 1         | 2         | 2016-03-01 | 5            |
| 1         | 2         | 2016-05-02 | 6            |
| 2         | 3         | 2017-06-25 | 1            |
| 3         | 1         | 2016-03-02 | 0            |
| 3         | 4         | 2018-07-03 | 5            |
+-----------+-----------+------------+--------------+
Output: 
+-----------+-------------+
| player_id | first_login |
+-----------+-------------+
| 1         | 2016-03-01  |
| 2         | 2017-06-25  |
| 3         | 2016-03-02  |
+-----------+-------------+

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■ 풀이

  문제 요구사항  

player_id 별로 가장 빠른  event_date를 first_login으로 출력해라.

>> player_id별로 event_date 최소일자를 출력한다. 정렬은 player_id 기준 오름차순

SELECT player_id, MIN(event_date) first_login
 FROM Activity
 GROUP BY 1
 ORDER BY 1;