【牛客】SQL125 得分不小于平均分的最低分

talle20212024-03-01 21:05

描述

请从试卷作答记录表中找到SQL试卷得分不小于该类试卷平均得分的用户最低得分。

示例数据 exam_record表（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 | 2020-01-02 09:01:01 | 2020-01-02 09:21:01 | 80 |
| 2 | 1002 | 9001 | 2021-09-05 19:01:01 | 2021-09-05 19:40:01 | 89 |
| 3 | 1002 | 9002 | 2021-09-02 12:01:01 | (NULL) | (NULL) |
| 4 | 1002 | 9003 | 2021-09-01 12:01:01 | (NULL) | (NULL) |
| 5 | 1002 | 9001 | 2021-02-02 19:01:01 | 2021-02-02 19:30:01 | 87 |
| 6 | 1002 | 9002 | 2021-05-05 18:01:01 | 2021-05-05 18:59:02 | 90 |
| 7 | 1003 | 9002 | 2021-02-06 12:01:01 | (NULL) | (NULL) |
| 8 | 1003 | 9003 | 2021-09-07 10:01:01 | 2021-09-07 10:31:01 | 86 |
| 9 | 1004 | 9003 | 2021-09-06 12:01:01 | (NULL) | (NULL) |

examination_info表（exam_id试卷ID, tag试卷类别, difficulty试卷难度, duration考试时长, release_time发布时间）

|----|---------|-----|------------|----------|---------------------|
| id | exam_id | tag | difficulty | duration | release_time |
| 1 | 9001 | SQL | hard | 60 | 2020-01-01 10:00:00 |
| 2 | 9002 | SQL | easy | 60 | 2020-02-01 10:00:00 |
| 3 | 9003 | 算法 | medium | 80 | 2020-08-02 10:00:00 |

示例输出数据：

|--------------------|
| min_score_over_avg |
| 87 |

解释：试卷9001和9002为SQL类别，作答这两份试卷的得分有 $80,89,87,90$ ，平均分为86.5，不小于平均分的最小分数为87

sql 复制代码

select min(score) from
exam_record left join examination_info using(exam_id)
where tag='SQL' and score is not null and
score>= (
    select avg(score) as avg_score from
    exam_record left join examination_info using(exam_id)
    where tag='SQL' and score is not null)