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leetcode-cn/problem (Chinese)/寻找忠实客户 [find-loyal-customers].html Normal file
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<p>表：<code>customer_transactions</code></p>
<pre>
+------------------+---------+
| Column Name | Type |
+------------------+---------+
| transaction_id | int |
| customer_id | int |
| transaction_date | date |
| amount | decimal |
| transaction_type | varchar |
+------------------+---------+
transaction_id 是这张表的唯一主键。
transaction_type 可以是 “purchase” 或 “refund”。
</pre>
<p>编写一个解决方案来查找 <strong>忠实客户</strong>。如果满足下述所有条件，可以认为该客户是 <strong>忠实</strong> 客户：</p>
<ul>
<li>进行了 <strong>至少</strong>&nbsp;<code><font face="monospace">3</font></code>&nbsp;次购买交易。</li>
<li>活跃了&nbsp;<strong>至少</strong>&nbsp;<code>30</code>&nbsp;天。</li>
<li>他们的 <strong>退款率</strong>&nbsp;少于&nbsp;<code>20%</code>。</li>
</ul>
<p>返回结果表以&nbsp;<code>customer_id</code> <strong>升序</strong>&nbsp;排序。</p>
<p>结果格式如下所示。</p>
<p>&nbsp;</p>
<p><strong class="example">示例：</strong></p>
<div class="example-block">
<p><strong>输入：</strong></p>
<p>customer_transactions 表：</p>
<pre class="example-io">
+----------------+-------------+------------------+--------+------------------+
| transaction_id | customer_id | transaction_date | amount | transaction_type |
+----------------+-------------+------------------+--------+------------------+
| 1 | 101 | 2024-01-05 | 150.00 | purchase |
| 2 | 101 | 2024-01-15 | 200.00 | purchase |
| 3 | 101 | 2024-02-10 | 180.00 | purchase |
| 4 | 101 | 2024-02-20 | 250.00 | purchase |
| 5 | 102 | 2024-01-10 | 100.00 | purchase |
| 6 | 102 | 2024-01-12 | 120.00 | purchase |
| 7 | 102 | 2024-01-15 | 80.00 | refund |
| 8 | 102 | 2024-01-18 | 90.00 | refund |
| 9 | 102 | 2024-02-15 | 130.00 | purchase |
| 10 | 103 | 2024-01-01 | 500.00 | purchase |
| 11 | 103 | 2024-01-02 | 450.00 | purchase |
| 12 | 103 | 2024-01-03 | 400.00 | purchase |
| 13 | 104 | 2024-01-01 | 200.00 | purchase |
| 14 | 104 | 2024-02-01 | 250.00 | purchase |
| 15 | 104 | 2024-02-15 | 300.00 | purchase |
| 16 | 104 | 2024-03-01 | 350.00 | purchase |
| 17 | 104 | 2024-03-10 | 280.00 | purchase |
| 18 | 104 | 2024-03-15 | 100.00 | refund |
+----------------+-------------+------------------+--------+------------------+
</pre>
<p><strong>输出：</strong></p>
<pre class="example-io">
+-------------+
| customer_id |
+-------------+
| 101 |
| 104 |
+-------------+
</pre>
<p><strong>解释：</strong></p>
<ul>
<li><strong>客户 101</strong>:
<ul>
<li>购买交易：4 (IDs: 1, 2, 3, 4)&nbsp;</li>
<li>退款交易：0</li>
<li>退款率：0/4 = 0%（少于 20%）</li>
<li>活跃时期：1 月&nbsp;5 日到 2 月 20 日 = 46 天（至少 30 天）</li>
<li>符合忠诚客户条件</li>
</ul>
</li>
<li><strong>客户 102</strong>:
<ul>
<li>购买交易：3 (IDs: 5, 6, 9)&nbsp;</li>
<li>退款交易：2 (IDs: 7, 8)</li>
<li>退款率：2/5 = 40% (超过&nbsp;20%)&nbsp;</li>
<li>不符合忠诚客户条件</li>
</ul>
</li>
<li><strong>客户 103</strong>:
<ul>
<li>购买交易：3 (IDs: 10, 11, 12)&nbsp;</li>
<li>退款交易：0</li>
<li>退款率：0/3 = 0%（少于 20%）</li>
<li>活跃时期：1 月 1 日到 1 月 3 日 =&nbsp;2 天（少于 30 天）</li>
<li>不符合忠诚客户条件</li>
</ul>
</li>
<li><strong>客户 104</strong>:
<ul>
<li>购买交易：5 (IDs: 13, 14, 15, 16, 17)&nbsp;</li>
<li>退款交易：1 (ID: 18)</li>
<li>退款率：1/6 = 16.67%（少于 20%）</li>
<li>活跃时期：1 月 1 日到 3 月 15 日 = 73 天（至少 30 天）</li>
<li>符合忠诚客户条件</li>
</ul>
</li>
</ul>
<p>结果表以 customer_id 升序排序。</p>
</div>