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57 lines
1.7 KiB
HTML
57 lines
1.7 KiB
HTML
<p>Table: <code>Teacher</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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| teacher_id | int |
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| subject_id | int |
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| dept_id | int |
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+-------------+------+
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(subject_id, dept_id) is the primary key (combinations of columns with unique values) of this table.
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Each row in this table indicates that the teacher with teacher_id teaches the subject subject_id in the department dept_id.
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</pre>
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<p> </p>
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<p>Write a solution to calculate the number of unique subjects each teacher teaches in the university.</p>
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<p>Return the result table in <strong>any order</strong>.</p>
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<p>The result format is shown in the following example.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong>
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Teacher table:
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+------------+------------+---------+
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| teacher_id | subject_id | dept_id |
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+------------+------------+---------+
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| 1 | 2 | 3 |
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| 1 | 2 | 4 |
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| 1 | 3 | 3 |
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| 2 | 1 | 1 |
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| 2 | 2 | 1 |
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| 2 | 3 | 1 |
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| 2 | 4 | 1 |
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+------------+------------+---------+
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<strong>Output:</strong>
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+------------+-----+
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| teacher_id | cnt |
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+------------+-----+
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| 1 | 2 |
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| 2 | 4 |
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+------------+-----+
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<strong>Explanation:</strong>
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Teacher 1:
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- They teach subject 2 in departments 3 and 4.
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- They teach subject 3 in department 3.
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Teacher 2:
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- They teach subject 1 in department 1.
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- They teach subject 2 in department 1.
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- They teach subject 3 in department 1.
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- They teach subject 4 in department 1.
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</pre>
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