LeetCode 2356: Number of Unique Subjects Taught by Each Teacher Solution
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2356. Number of Unique Subjects Taught by Each Teacher
Problem Explanation
Explanation:
To solve this problem, we need to count the number of unique subjects each teacher teaches. We can achieve this by grouping the data by teacher_id and then counting the distinct subject_ids for each teacher.
- Group the data by teacher_id.
- Count the number of unique subject_ids for each teacher.
- Return the result table with teacher_id and the count of unique subjects they teach.
Time Complexity: O(n), where n is the number of rows in the Teacher table. Space Complexity: O(n), for storing the result.
:
Solution Code
# Write your Java solution here
SELECT teacher_id, COUNT(DISTINCT subject_id) AS cnt
FROM Teacher
GROUP BY teacher_id;Try It Yourself
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