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132 lines
4.6 KiB
HTML
132 lines
4.6 KiB
HTML
<p>Table: <code>patients</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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| patient_id | int |
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| patient_name| varchar |
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| age | int |
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+-------------+---------+
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patient_id is the unique identifier for this table.
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Each row contains information about a patient.
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</pre>
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<p>Table: <code>covid_tests</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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| test_id | int |
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| patient_id | int |
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| test_date | date |
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| result | varchar |
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+-------------+---------+
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test_id is the unique identifier for this table.
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Each row represents a COVID test result. The result can be Positive, Negative, or Inconclusive.
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</pre>
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<p>Write a solution to find patients who have <strong>recovered from COVID</strong> - patients who tested positive but later tested negative.</p>
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<ul>
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<li>A patient is considered recovered if they have <strong>at least one</strong> <strong>Positive</strong> test followed by at least one <strong>Negative</strong> test on a <strong>later date</strong></li>
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<li>Calculate the <strong>recovery time</strong> in days as the <strong>difference</strong> between the <strong>first positive test</strong> and the <strong>first negative test</strong> after that <strong>positive test</strong></li>
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<li><strong>Only include</strong> patients who have both positive and negative test results</li>
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</ul>
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<p>Return <em>the result table ordered by </em><code>recovery_time</code><em> in <strong>ascending</strong> order, then by </em><code>patient_name</code><em> in <strong>ascending</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>patients table:</p>
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<pre class="example-io">
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+------------+--------------+-----+
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| patient_id | patient_name | age |
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+------------+--------------+-----+
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| 1 | Alice Smith | 28 |
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| 2 | Bob Johnson | 35 |
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| 3 | Carol Davis | 42 |
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| 4 | David Wilson | 31 |
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| 5 | Emma Brown | 29 |
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+------------+--------------+-----+
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</pre>
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<p>covid_tests table:</p>
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<pre class="example-io">
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+---------+------------+------------+--------------+
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| test_id | patient_id | test_date | result |
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+---------+------------+------------+--------------+
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| 1 | 1 | 2023-01-15 | Positive |
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| 2 | 1 | 2023-01-25 | Negative |
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| 3 | 2 | 2023-02-01 | Positive |
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| 4 | 2 | 2023-02-05 | Inconclusive |
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| 5 | 2 | 2023-02-12 | Negative |
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| 6 | 3 | 2023-01-20 | Negative |
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| 7 | 3 | 2023-02-10 | Positive |
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| 8 | 3 | 2023-02-20 | Negative |
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| 9 | 4 | 2023-01-10 | Positive |
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| 10 | 4 | 2023-01-18 | Positive |
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| 11 | 5 | 2023-02-15 | Negative |
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| 12 | 5 | 2023-02-20 | Negative |
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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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| patient_id | patient_name | age | recovery_time |
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+------------+--------------+-----+---------------+
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| 1 | Alice Smith | 28 | 10 |
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| 3 | Carol Davis | 42 | 10 |
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| 2 | Bob Johnson | 35 | 11 |
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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 Smith (patient_id = 1):</strong>
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<ul>
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<li>First positive test: 2023-01-15</li>
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<li>First negative test after positive: 2023-01-25</li>
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<li>Recovery time: 25 - 15 = 10 days</li>
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</ul>
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</li>
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<li><strong>Bob Johnson (patient_id = 2):</strong>
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<ul>
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<li>First positive test: 2023-02-01</li>
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<li>Inconclusive test on 2023-02-05 (ignored for recovery calculation)</li>
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<li>First negative test after positive: 2023-02-12</li>
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<li>Recovery time: 12 - 1 = 11 days</li>
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</ul>
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</li>
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<li><strong>Carol Davis (patient_id = 3):</strong>
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<ul>
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<li>Had negative test on 2023-01-20 (before positive test)</li>
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<li>First positive test: 2023-02-10</li>
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<li>First negative test after positive: 2023-02-20</li>
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<li>Recovery time: 20 - 10 = 10 days</li>
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</ul>
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</li>
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<li><strong>Patients not included:</strong>
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<ul>
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<li>David Wilson (patient_id = 4): Only has positive tests, no negative test after positive</li>
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<li>Emma Brown (patient_id = 5): Only has negative tests, never tested positive</li>
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</ul>
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</li>
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</ul>
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<p>Output table is ordered by recovery_time in ascending order, and then by patient_name in ascending order.</p>
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</div>
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