| title | category | tag | ||
|---|---|---|---|---|
Summary of Common SQL Interview Questions (3) |
Database |
|
Source of questions: Niuke Question Bank - SQL Advanced Challenge
You can decide whether to skip difficult or challenging questions based on your actual situation and interview needs.
Description: The operations team at Niuke wants to see the score situation of users on high-difficulty SQL papers.
Please help her calculate the truncated average score (the average after removing one maximum and one minimum score) of all users who completed high-difficulty SQL papers from the exam_record data table.
Sample data: examination_info (exam_id Paper ID, tag Paper Category, difficulty Paper Difficulty, duration Exam Duration, release_time Release Time)
| id | exam_id | tag | difficulty | duration | release_time |
|---|---|---|---|---|---|
| 1 | 9001 | SQL | hard | 60 | 2020-01-01 10:00:00 |
| 2 | 9002 | Algorithm | medium | 80 | 2020-08-02 10:00:00 |
Sample data: exam_record (uid User ID, exam_id Paper ID, start_time Start Time, submit_time Submit Time, score Score)
| id | uid | exam_id | start_time | submit_time | score |
|---|---|---|---|---|---|
| 1 | 1001 | 9001 | 2020-01-02 09:01:01 | 2020-01-02 09:21:01 | 80 |
| 2 | 1001 | 9001 | 2021-05-02 10:01:01 | 2021-05-02 10:30:01 | 81 |
| 3 | 1001 | 9001 | 2021-06-02 19:01:01 | 2021-06-02 19:31:01 | 84 |
| 4 | 1001 | 9002 | 2021-09-05 19:01:01 | 2021-09-05 19:40:01 | 89 |
| 5 | 1001 | 9001 | 2021-09-02 12:01:01 | (NULL) | (NULL) |
| 6 | 1001 | 9002 | 2021-09-01 12:01:01 | (NULL) | (NULL) |
| 7 | 1002 | 9002 | 2021-02-02 19:01:01 | 2021-02-02 19:30:01 | 87 |
| 8 | 1002 | 9001 | 2021-05-05 18:01:01 | 2021-05-05 18:59:02 | 90 |
| 9 | 1003 | 9001 | 2021-09-07 12:01:01 | 2021-09-07 10:31:01 | 50 |
| 10 | 1004 | 9001 | 2021-09-06 10:01:01 | (NULL) | (NULL) |
Based on your input, your query result is as follows:
| tag | difficulty | clip_avg_score |
|---|---|---|
| SQL | hard | 81.7 |
From the examination_info table, it can be seen that paper 9001 is a high-difficulty SQL paper, and the scores for this paper are [80, 81, 84, 90, 50]. After removing the highest and lowest scores, we have [80, 81, 84], and the average score is 81.6666667, which rounds to 81.7 when keeping one decimal place.
Input Description:
The input data must contain at least 3 valid scores.
Approach 1: To find high-difficulty SQL papers, you need to join the examination_info table and find the high-difficulty courses. From examination_info, we know that the exam_id for high-difficulty SQL is 900