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30 changes: 15 additions & 15 deletions docs/database/sql/sql-questions-04.md
Original file line number Diff line number Diff line change
Expand Up @@ -142,28 +142,28 @@ WHERE ranking <= 3

试卷作答记录表 `exam_record`(`uid` 用户 ID, `exam_id` 试卷 ID, `start_time` 开始作答时间, `submit_time` 交卷时间, `score` 得分):

| id | uid | exam_id | start_time | submit_time | score |
| --- | ---- | ------- | ------------------- | ------------------- | ------ |
| 1 | 1001 | 9001 | 2021-09-01 09:01:01 | 2021-09-01 09:51:01 | 78 |
| 2 | 1001 | 9002 | 2021-09-01 09:01:01 | 2021-09-01 09:31:00 | 81 |
| 3 | 1002 | 9002 | 2021-09-01 12:01:01 | 2021-09-01 12:31:01 | 81 |
| 4 | 1003 | 9001 | 2021-09-01 19:01:01 | 2021-09-01 19:59:01 | 86 |
| 5 | 1003 | 9002 | 2021-09-01 12:01:01 | 2021-09-01 12:31:51 | 89 |
| 6 | 1004 | 9002 | 2021-09-01 19:01:01 | 2021-09-01 19:30:01 | 85 |
| 7 | 1005 | 9001 | 2021-09-01 12:01:01 | 2021-09-01 12:31:02 | 85 |
| 8 | 1006 | 9001 | 2021-09-07 10:01:01 | 2021-09-07 10:21:01 | 84 |
| 9 | 1003 | 9001 | 2021-09-08 12:01:01 | 2021-09-08 12:11:01 | 40 |
| 10 | 1003 | 9002 | 2021-09-01 14:01:01 | (NULL) | (NULL) |
| 11 | 1005 | 9001 | 2021-09-01 14:01:01 | (NULL) | (NULL) |
| 12 | 1003 | 9003 | 2021-09-08 15:01:01 | (NULL) | (NULL) |
| id | uid | exam_id | start_time | submit_time | score |
| ---- | ---- | ------- | ------------------- | ------------------- | ------ |
| 1 | 1001 | 9001 | 2021-09-01 09:01:01 | 2021-09-01 09:51:01 | 78 |
| 2 | 1001 | 9002 | 2021-09-01 09:01:01 | 2021-09-01 09:31:00 | 81 |
| 3 | 1002 | 9002 | 2021-09-01 12:01:01 | 2021-09-01 12:31:01 | 81 |
| 4 | 1003 | 9001 | 2021-09-01 19:01:01 | 2021-09-01 19:59:01 | 86 |
| 5 | 1003 | 9002 | 2021-09-01 12:01:01 | 2021-09-01 12:31:51 | 89 |
| 6 | 1004 | 9002 | 2021-09-01 19:01:01 | 2021-09-01 19:30:01 | 85 |
| 7 | 1005 | 9001 | 2021-09-01 12:01:01 | 2021-09-01 12:31:02 | 85 |
| 8 | 1006 | 9001 | 2021-09-07 10:02:01 | 2021-09-07 10:21:01 | 84 |
| 9 | 1003 | 9001 | 2021-09-08 12:01:01 | 2021-09-08 12:11:01 | 40 |
| 10 | 1003 | 9002 | 2021-09-01 14:01:01 | (NULL) | (NULL) |
| 11 | 1005 | 9001 | 2021-09-01 14:01:01 | (NULL) | (NULL) |
| 12 | 1003 | 9003 | 2021-09-08 15:01:01 | (NULL) | (NULL) |

找到第二快和第二慢用时之差大于试卷时长的一半的试卷信息,按试卷 ID 降序排序。由示例数据结果输出如下:

| exam_id | duration | release_time |
| ------- | -------- | ------------------- |
| 9001 | 60 | 2021-09-01 06:00:00 |

**解释**:试卷 9001 被作答用时有 50 分钟、50 分钟、30 分 1 秒、11 分钟、10 分钟,第二快和第二慢用时之差为 50 分钟-11 分钟=39 分钟,试卷时长为 60 分钟,因此满足大于试卷时长一半的条件,输出试卷 ID、时长、发布时间。
**解释**:试卷 9001 被作答用时有 50 分钟、58 分钟、30 分 1 秒、19 分钟、10 分钟,第二快和第二慢用时之差为 50 分钟-19 分钟=31 分钟,试卷时长为 60 分钟,因此满足大于试卷时长一半的条件,输出试卷 ID、时长、发布时间。

**思路:**

Expand Down