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81 lines
2.8 KiB
HTML
81 lines
2.8 KiB
HTML
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<p>表: <code>Signups</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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| user_id | int |
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| time_stamp | datetime |
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+----------------+----------+
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User_id是该表的主键。
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每一行都包含ID为user_id的用户的注册时间信息。
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</pre>
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<p> </p>
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<p>表: <code>Confirmations</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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| user_id | int |
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| time_stamp | datetime |
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| action | ENUM |
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+----------------+----------+
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(user_id, time_stamp)是该表的主键。
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user_id是一个引用到注册表的外键。
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action是类型为('confirmed'， 'timeout')的ENUM
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该表的每一行都表示ID为user_id的用户在time_stamp请求了一条确认消息，该确认消息要么被确认('confirmed')，要么被过期('timeout')。
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</pre>
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<p> </p>
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<p>用户的 <strong>确认率</strong> 是 <code>'confirmed'</code> 消息的数量除以请求的确认消息的总数。没有请求任何确认消息的用户的确认率为 <code>0</code> 。确认率四舍五入到 <strong>小数点后两位</strong> 。</p>
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<p>编写一个SQL查询来查找每个用户的 确认率 。<br />
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<br />
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以 任意顺序 返回结果表。<br />
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<br />
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查询结果格式如下所示。<br />
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<br />
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<strong>示例1:</strong></p>
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<pre>
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<b>输入：</b>
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Signups 表:
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+---------+---------------------+
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| user_id | time_stamp |
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+---------+---------------------+
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| 3 | 2020-03-21 10:16:13 |
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| 7 | 2020-01-04 13:57:59 |
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| 2 | 2020-07-29 23:09:44 |
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| 6 | 2020-12-09 10:39:37 |
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+---------+---------------------+
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Confirmations 表:
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+---------+---------------------+-----------+
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| user_id | time_stamp | action |
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+---------+---------------------+-----------+
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| 3 | 2021-01-06 03:30:46 | timeout |
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| 3 | 2021-07-14 14:00:00 | timeout |
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| 7 | 2021-06-12 11:57:29 | confirmed |
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| 7 | 2021-06-13 12:58:28 | confirmed |
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| 7 | 2021-06-14 13:59:27 | confirmed |
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| 2 | 2021-01-22 00:00:00 | confirmed |
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| 2 | 2021-02-28 23:59:59 | timeout |
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+---------+---------------------+-----------+
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<strong>输出:</strong>
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+---------+-------------------+
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| user_id | confirmation_rate |
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+---------+-------------------+
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| 6 | 0.00 |
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| 3 | 0.00 |
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| 7 | 1.00 |
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| 2 | 0.50 |
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+---------+-------------------+
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<strong>解释:
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</strong>用户 6 没有请求任何确认消息。确认率为 0。
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用户 3 进行了 2 次请求，都超时了。确认率为 0。
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用户 7 提出了 3 个请求，所有请求都得到了确认。确认率为 1。
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用户 2 做了 2 个请求，其中一个被确认，另一个超时。确认率为 1 / 2 = 0.5。</pre>
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