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139 lines
6.3 KiB
HTML
139 lines
6.3 KiB
HTML
<p>Table: <code>students</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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| student_id | int |
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| student_name | varchar |
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| major | varchar |
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+--------------+---------+
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student_id is the unique identifier for this table.
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Each row contains information about a student and their academic major.
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</pre>
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<p>Table: <code>study_sessions</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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| session_id | int |
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| student_id | int |
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| subject | varchar |
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| session_date | date |
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| hours_studied | decimal |
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+---------------+---------+
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session_id is the unique identifier for this table.
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Each row represents a study session by a student for a specific subject.
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</pre>
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<p>Write a solution to find students who follow the <strong>Study Spiral Pattern</strong> - students who consistently study multiple subjects in a rotating cycle.</p>
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<ul>
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<li>A Study Spiral Pattern means a student studies at least <code>3</code><strong> different subjects</strong> in a repeating sequence</li>
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<li>The pattern must repeat for <strong>at least </strong><code>2</code><strong> complete cycles</strong> (minimum <code>6</code> study sessions)</li>
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<li>Sessions must be <strong>consecutive dates</strong> with no gaps longer than <code>2</code> days between sessions</li>
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<li>Calculate the <strong>cycle length</strong> (number of different subjects in the pattern)</li>
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<li>Calculate the <strong>total study hours</strong> across all sessions in the pattern</li>
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<li>Only include students with cycle length of <strong>at least </strong><code>3</code><strong> subjects</strong></li>
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</ul>
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<p>Return <em>the result table ordered by cycle length in <strong>descending</strong> order, then by total study hours in <strong>descending</strong> order</em>.</p>
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<p>The result format is in the following example.</p>
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<p> </p>
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<p><strong class="example">Example:</strong></p>
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<div class="example-block">
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<p><strong>Input:</strong></p>
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<p>students table:</p>
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<pre class="example-io">
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+------------+--------------+------------------+
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| student_id | student_name | major |
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+------------+--------------+------------------+
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| 1 | Alice Chen | Computer Science |
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| 2 | Bob Johnson | Mathematics |
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| 3 | Carol Davis | Physics |
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| 4 | David Wilson | Chemistry |
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| 5 | Emma Brown | Biology |
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+------------+--------------+------------------+
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</pre>
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<p>study_sessions table:</p>
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<pre class="example-io">
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+------------+------------+------------+--------------+---------------+
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| session_id | student_id | subject | session_date | hours_studied |
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+------------+------------+------------+--------------+---------------+
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| 1 | 1 | Math | 2023-10-01 | 2.5 |
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| 2 | 1 | Physics | 2023-10-02 | 3.0 |
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| 3 | 1 | Chemistry | 2023-10-03 | 2.0 |
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| 4 | 1 | Math | 2023-10-04 | 2.5 |
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| 5 | 1 | Physics | 2023-10-05 | 3.0 |
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| 6 | 1 | Chemistry | 2023-10-06 | 2.0 |
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| 7 | 2 | Algebra | 2023-10-01 | 4.0 |
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| 8 | 2 | Calculus | 2023-10-02 | 3.5 |
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| 9 | 2 | Statistics | 2023-10-03 | 2.5 |
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| 10 | 2 | Geometry | 2023-10-04 | 3.0 |
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| 11 | 2 | Algebra | 2023-10-05 | 4.0 |
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| 12 | 2 | Calculus | 2023-10-06 | 3.5 |
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| 13 | 2 | Statistics | 2023-10-07 | 2.5 |
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| 14 | 2 | Geometry | 2023-10-08 | 3.0 |
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| 15 | 3 | Biology | 2023-10-01 | 2.0 |
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| 16 | 3 | Chemistry | 2023-10-02 | 2.5 |
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| 17 | 3 | Biology | 2023-10-03 | 2.0 |
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| 18 | 3 | Chemistry | 2023-10-04 | 2.5 |
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| 19 | 4 | Organic | 2023-10-01 | 3.0 |
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| 20 | 4 | Physical | 2023-10-05 | 2.5 |
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+------------+------------+------------+--------------+---------------+
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</pre>
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<p><strong>Output:</strong></p>
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<pre class="example-io">
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+------------+--------------+------------------+--------------+-------------------+
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| student_id | student_name | major | cycle_length | total_study_hours |
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+------------+--------------+------------------+--------------+-------------------+
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| 2 | Bob Johnson | Mathematics | 4 | 26.0 |
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| 1 | Alice Chen | Computer Science | 3 | 15.0 |
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+------------+--------------+------------------+--------------+-------------------+
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</pre>
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<p><strong>Explanation:</strong></p>
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<ul>
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<li><strong>Alice Chen (student_id = 1):</strong>
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<ul>
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<li>Study sequence: Math → Physics → Chemistry → Math → Physics → Chemistry</li>
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<li>Pattern: 3 subjects (Math, Physics, Chemistry) repeating for 2 complete cycles</li>
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<li>Consecutive dates: Oct 1-6 with no gaps > 2 days</li>
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<li>Cycle length: 3 subjects</li>
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<li>Total hours: 2.5 + 3.0 + 2.0 + 2.5 + 3.0 + 2.0 = 15.0 hours</li>
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</ul>
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</li>
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<li><strong>Bob Johnson (student_id = 2):</strong>
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<ul>
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<li>Study sequence: Algebra → Calculus → Statistics → Geometry → Algebra → Calculus → Statistics → Geometry</li>
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<li>Pattern: 4 subjects (Algebra, Calculus, Statistics, Geometry) repeating for 2 complete cycles</li>
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<li>Consecutive dates: Oct 1-8 with no gaps > 2 days</li>
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<li>Cycle length: 4 subjects</li>
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<li>Total hours: 4.0 + 3.5 + 2.5 + 3.0 + 4.0 + 3.5 + 2.5 + 3.0 = 26.0 hours</li>
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</ul>
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</li>
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<li><strong>Students not included:</strong>
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<ul>
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<li>Carol Davis (student_id = 3): Only 2 subjects (Biology, Chemistry) - doesn't meet minimum 3 subjects requirement</li>
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<li>David Wilson (student_id = 4): Only 2 study sessions with a 4-day gap - doesn't meet consecutive dates requirement</li>
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<li>Emma Brown (student_id = 5): No study sessions recorded</li>
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</ul>
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</li>
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</ul>
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<p>The result table is ordered by cycle_length in descending order, then by total_study_hours in descending order.</p>
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</div>
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