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44 lines
1.4 KiB
HTML
44 lines
1.4 KiB
HTML
<p>活动表 <code>Activity</code>：</p>
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<pre>
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+--------------+---------+
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| Column Name | Type |
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+--------------+---------+
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| player_id | int |
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| device_id | int |
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| event_date | date |
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| games_played | int |
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+--------------+---------+
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在 SQL 中，表的主键是 (player_id, event_date)。
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这张表展示了一些游戏玩家在游戏平台上的行为活动。
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每行数据记录了一名玩家在退出平台之前，当天使用同一台设备登录平台后打开的游戏的数目（可能是 0 个）。
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</pre>
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<p> </p>
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<p>查询每位玩家 <strong>第一次登陆平台的日期</strong>。</p>
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<p>查询结果的格式如下所示：</p>
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<pre>
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Activity 表：
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+-----------+-----------+------------+--------------+
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| player_id | device_id | event_date | games_played |
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+-----------+-----------+------------+--------------+
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| 1 | 2 | 2016-03-01 | 5 |
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| 1 | 2 | 2016-05-02 | 6 |
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| 2 | 3 | 2017-06-25 | 1 |
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| 3 | 1 | 2016-03-02 | 0 |
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| 3 | 4 | 2018-07-03 | 5 |
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+-----------+-----------+------------+--------------+
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Result 表：
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+-----------+-------------+
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| player_id | first_login |
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+-----------+-------------+
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| 1 | 2016-03-01 |
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| 2 | 2017-06-25 |
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| 3 | 2016-03-02 |
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+-----------+-------------+
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</pre>
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