README.md

550. 游戏玩法分析 IV

English Version

题目描述

Table: Activity

+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| player_id    | int     |
| device_id    | int     |
| event_date   | date    |
| games_played | int     |
+--------------+---------+
（player_id，event_date）是此表的主键（具有唯一值的列的组合）。
这张表显示了某些游戏的玩家的活动情况。
每一行是一个玩家的记录，他在某一天使用某个设备注销之前登录并玩了很多游戏（可能是 0）。

 

编写解决方案，报告在首次登录的第二天再次登录的玩家的 比率，四舍五入到小数点后两位。换句话说，你需要计算从首次登录日期开始至少连续两天登录的玩家的数量，然后除以玩家总数。

结果格式如下所示：

 

示例 1：

输入：
Activity table:
+-----------+-----------+------------+--------------+
| player_id | device_id | event_date | games_played |
+-----------+-----------+------------+--------------+
| 1         | 2         | 2016-03-01 | 5            |
| 1         | 2         | 2016-03-02 | 6            |
| 2         | 3         | 2017-06-25 | 1            |
| 3         | 1         | 2016-03-02 | 0            |
| 3         | 4         | 2018-07-03 | 5            |
+-----------+-----------+------------+--------------+
输出：
+-----------+
| fraction  |
+-----------+
| 0.33      |
+-----------+
解释：
只有 ID 为 1 的玩家在第一天登录后才重新登录，所以答案是 1/3 = 0.33

解法

SQL

# Write your MySQL query statement below
SELECT round(AVG(b.event_date IS NOT NULL), 2) AS fraction
FROM
    (
        SELECT
            player_id,
            MIN(event_date) AS event_date
        FROM activity
        GROUP BY player_id
    ) AS a
    LEFT JOIN activity AS b
        ON a.player_id = b.player_id AND DATEDIFF(a.event_date, b.event_date) = -1;

# Write your MySQL query statement below
WITH
    T AS (
        SELECT
            player_id,
            datediff(
                lead(event_date) OVER (
                    PARTITION BY player_id
                    ORDER BY event_date
                ),
                event_date
            ) AS diff,
            row_number() OVER (
                PARTITION BY player_id
                ORDER BY event_date
            ) AS rk
        FROM Activity
    )
SELECT
    round(
        count(DISTINCT if(diff = 1, player_id, NULL)) / count(
            DISTINCT player_id
        ),
        2
    ) AS fraction
FROM T
WHERE rk = 1;