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134 lines
5.6 KiB
HTML
134 lines
5.6 KiB
HTML
<p>表：<code>library_books</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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| book_id | int |
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| title | varchar |
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| author | varchar |
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| genre | varchar |
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| publication_year | int |
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| total_copies | int |
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+------------------+---------+
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book_id 是这张表的唯一主键。
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每一行包含图书馆中一本书的信息，包括图书馆拥有的副本总数。
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</pre>
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<p>表：<code>borrowing_records</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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| record_id | int |
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| book_id | int |
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| borrower_name | varchar |
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| borrow_date | date |
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| return_date | date |
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+---------------+---------+
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record_id 是这张表的唯一主键。
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每一行代表一笔借阅交易并且如果这本书目前被借出并且还没有被归还，return_date 为 NULL。
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</pre>
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<p>编写一个解决方案以找到 <strong>所有</strong> <strong>当前被借出（未归还） </strong>且图书馆中 <strong>无可用副本</strong> 的书籍。</p>
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<ul>
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<li>如果存在一条借阅记录，其 <code>return_date</code> 为 <strong>NULL</strong>，那么这本书被认为 <strong>当前是借出的</strong>。</li>
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</ul>
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<p>返回结果表按当前借阅者数量 <strong>降序</strong> 排列，然后按书名 <strong>升序</strong> 排列。</p>
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<p>结果格式如下所示。</p>
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<p> </p>
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<p><strong class="example">示例：</strong></p>
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<div class="example-block">
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<p><strong>输入：</strong></p>
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<p>library_books 表：</p>
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<pre class="example-io">
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+---------+------------------------+------------------+----------+------------------+--------------+
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| book_id | title | author | genre | publication_year | total_copies |
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+---------+------------------------+------------------+----------+------------------+--------------+
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| 1 | The Great Gatsby | F. Scott | Fiction | 1925 | 3 |
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| 2 | To Kill a Mockingbird | Harper Lee | Fiction | 1960 | 3 |
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| 3 | 1984 | George Orwell | Dystopian| 1949 | 1 |
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| 4 | Pride and Prejudice | Jane Austen | Romance | 1813 | 2 |
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| 5 | The Catcher in the Rye | J.D. Salinger | Fiction | 1951 | 1 |
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| 6 | Brave New World | Aldous Huxley | Dystopian| 1932 | 4 |
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+---------+------------------------+------------------+----------+------------------+--------------+
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</pre>
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<p>borrowing_records 表：</p>
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<pre class="example-io">
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+-----------+---------+---------------+-------------+-------------+
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| record_id | book_id | borrower_name | borrow_date | return_date |
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+-----------+---------+---------------+-------------+-------------+
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| 1 | 1 | Alice Smith | 2024-01-15 | NULL |
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| 2 | 1 | Bob Johnson | 2024-01-20 | NULL |
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| 3 | 2 | Carol White | 2024-01-10 | 2024-01-25 |
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| 4 | 3 | David Brown | 2024-02-01 | NULL |
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| 5 | 4 | Emma Wilson | 2024-01-05 | NULL |
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| 6 | 5 | Frank Davis | 2024-01-18 | 2024-02-10 |
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| 7 | 1 | Grace Miller | 2024-02-05 | NULL |
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| 8 | 6 | Henry Taylor | 2024-01-12 | NULL |
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| 9 | 2 | Ivan Clark | 2024-02-12 | NULL |
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| 10 | 2 | Jane Adams | 2024-02-15 | NULL |
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+-----------+---------+---------------+-------------+-------------+
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</pre>
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<p><strong>输出：</strong></p>
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<pre class="example-io">
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+---------+------------------+---------------+-----------+------------------+-------------------+
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| book_id | title | author | genre | publication_year | current_borrowers |
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+---------+------------------+---------------+-----------+------------------+-------------------+
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| 1 | The Great Gatsby | F. Scott | Fiction | 1925 | 3 |
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| 3 | 1984 | George Orwell | Dystopian | 1949 | 1 |
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+---------+------------------+---------------+-----------+------------------+-------------------+
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</pre>
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<p><strong>解释：</strong></p>
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<ul>
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<li><strong>The Great Gatsby (book_id = 1)：</strong>
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<ul>
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<li>总副本数：3</li>
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<li>当前被 Alice Smith，Bob Johnson 和 Grace Miller 借阅（3 名借阅者）</li>
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<li>可用副本数：3 - 3 = 0</li>
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<li>因为 available_copies = 0，所以被包含</li>
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</ul>
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</li>
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<li><strong>1984 (book_id = 3):</strong>
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<ul>
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<li>总副本数：1</li>
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<li>当前被 David Brown 借阅（1 名借阅者）</li>
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<li>可用副本数：1 - 1 = 0</li>
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<li>因为 available_copies = 0，所以被包含</li>
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</ul>
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</li>
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<li><strong>未被包含的书：</strong>
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<ul>
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<li>To Kill a Mockingbird (book_id = 2)：总副本数 = 3，当前借阅者 = 2，可用副本 = 1</li>
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<li>Pride and Prejudice (book_id = 4)：总副本数 = 2，当前借阅者 = 1，可用副本 = 1</li>
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<li>The Catcher in the Rye (book_id = 5)：总副本数 = 1，当前借阅者 = 0，可用副本 = 1</li>
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<li>Brave New World (book_id = 6)：总副本数 = 4，当前借阅者 = 1，可用副本 = 3</li>
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</ul>
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</li>
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<li><strong>结果顺序：</strong>
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<ul>
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<li>The Great Gatsby 有 3 名当前借阅者，排序第一</li>
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<li>1984 有 1 名当前借阅者，排序第二</li>
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</ul>
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</li>
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</ul>
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<p>输出表以 current_borrowers 降序排序，然后以 book_title 升序排序。</p>
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</div>
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