当前位置：网站首页>数据库系统原理与应用教程（069）—— MySQL 练习题：操作题 95-100（十三）：分组查询与聚合函数的使用
数据库系统原理与应用教程（069）—— MySQL 练习题：操作题 95-100（十三）：分组查询与聚合函数的使用
2022-07-30 17:26:00 【睿思达DBA_WGX】
数据库系统原理与应用教程（069）—— MySQL 练习题：操作题 95-100（十三）：分组查询与聚合函数的使用
95、聚合函数的使用（1）
数据表：examination_info（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），表中数据如下：
| id | exam_id | tag | difficulty | duration | release_time |
|---|---|---|---|---|---|
| 1 | 9001 | SQL | hard | 60 | 2020-01-01 10:00:00 |
| 2 | 9002 | 算法 | medium | 80 | 2020-08-02 10:00:00 |
数据表：exam_record（uid：用户ID，exam_id：试卷ID，start_time：开始答题时间，submit_time：交卷时间，score：得分），表中数据如下：
| 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) |
【问题】从 exam_record 数据表中计算所有用户完成 SQL 类别高难度试卷得分的截断平均值（去掉一个最大值和一个最小值后的平均值）。查询结果如下：
| tag | difficulty | clip_avg_score |
|---|---|---|
| SQL | hard | 81.7 |
数据表：exam_record，表结构和数据如下：
/* drop table if exists examination_info; CREATE TABLE examination_info ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', exam_id int UNIQUE NOT NULL COMMENT '试卷ID', tag varchar(32) COMMENT '类别标签', difficulty varchar(8) COMMENT '难度', duration int NOT NULL COMMENT '时长', release_time datetime COMMENT '发布时间' )CHARACTER SET utf8 COLLATE utf8_general_ci; drop table if exists exam_record; CREATE TABLE exam_record ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', uid int NOT NULL COMMENT '用户ID', exam_id int NOT NULL COMMENT '试卷ID', start_time datetime NOT NULL COMMENT '开始时间', submit_time datetime COMMENT '提交时间', score tinyint COMMENT '得分' )CHARACTER SET utf8 COLLATE utf8_general_ci; INSERT INTO examination_info(exam_id,tag,difficulty,duration,release_time) VALUES (9001, 'SQL', 'hard', 60, '2020-01-01 10:00:00'), (9002, '算法', 'medium', 80, '2020-08-02 10:00:00'); INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES (1001, 9001, '2020-01-02 09:01:01', '2020-01-02 09:21:01', 80), (1001, 9001, '2021-05-02 10:01:01', '2021-05-02 10:30:01', 81), (1001, 9001, '2021-06-02 19:01:01', '2021-06-02 19:31:01', 84), (1001, 9002, '2021-09-05 19:01:01', '2021-09-05 19:40:01', 89), (1001, 9001, '2021-09-02 12:01:01', null, null), (1001, 9002, '2021-09-01 12:01:01', null, null), (1002, 9002, '2021-02-02 19:01:01', '2021-02-02 19:30:01', 87), (1002, 9001, '2021-05-05 18:01:01', '2021-05-05 18:59:02', 90), (1003, 9001, '2021-02-06 12:01:01', null, null), (1003, 9001, '2021-09-07 10:01:01', '2021-09-07 10:31:01', 50); */
解答：
/* select 'SQL' tag, 'hard' difficulty, round(avg(score),1) clip_avg_score from exam_record where exam_id in (select exam_id from examination_info where tag = 'SQL' and difficulty = 'hard') and score <> (select max(score) from exam_record where exam_id in (select exam_id from examination_info where tag = 'SQL' and difficulty = 'hard')) and score <> (select min(score) from exam_record where exam_id in (select exam_id from examination_info where tag = 'SQL' and difficulty = 'hard')); */
mysql> select 'SQL' tag, 'hard' difficulty,
-> round(avg(score),1) clip_avg_score from exam_record where exam_id in
-> (select exam_id from examination_info where tag = 'SQL' and difficulty = 'hard')
-> and score <>
-> (select max(score) from exam_record where exam_id in
-> (select exam_id from examination_info where tag = 'SQL' and difficulty = 'hard'))
-> and score <>
-> (select min(score) from exam_record where exam_id in
-> (select exam_id from examination_info where tag = 'SQL' and difficulty = 'hard'));
+-----+------------+----------------+
| tag | difficulty | clip_avg_score |
+-----+------------+----------------+
| SQL | hard | 81.7 |
+-----+------------+----------------+
1 row in set (0.01 sec)
96、聚合函数的使用（2）
数据表：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），表中数据如下：
| 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 | 2021-02-06 12:01:01 | (NULL) | (NULL) |
| 10 | 1003 | 9001 | 2021-09-07 10:01:01 | 2021-09-07 10:31:01 | 88 |
| 11 | 1004 | 9001 | 2021-09-06 12:01:01 | (NULL) | (NULL) |
【问题】请统计出总答题次数：total_pv、试卷已完成答题数：complete_pv，已完成的试卷数：complete_exam_cnt。查询结果如下：
| total_pv | complete_pv | complete_exam_cnt |
|---|---|---|
| 11 | 7 | 2 |
表结构和数据如下：
/* drop table if exists exam_record; CREATE TABLE exam_record ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', uid int NOT NULL COMMENT '用户ID', exam_id int NOT NULL COMMENT '试卷ID', start_time datetime NOT NULL COMMENT '开始时间', submit_time datetime COMMENT '提交时间', score tinyint COMMENT '得分' )CHARACTER SET utf8 COLLATE utf8_general_ci; INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES (1001, 9001, '2020-01-02 09:01:01', '2020-01-02 09:21:01', 80), (1001, 9001, '2021-05-02 10:01:01', '2021-05-02 10:30:01', 81), (1001, 9001, '2021-06-02 19:01:01', '2021-06-02 19:31:01', 84), (1001, 9002, '2021-09-05 19:01:01', '2021-09-05 19:40:01', 89), (1001, 9001, '2021-09-02 12:01:01', null, null), (1001, 9002, '2021-09-01 12:01:01', null, null), (1002, 9002, '2021-02-02 19:01:01', '2021-02-02 19:30:01', 87), (1002, 9001, '2021-05-05 18:01:01', '2021-05-05 18:59:02', 90), (1003, 9001, '2021-02-06 12:01:01', null, null), (1003, 9001, '2021-09-07 10:01:01', '2021-09-07 10:31:01', 89), (1004, 9001, '2021-09-06 12:01:01', null, null); */
解答：
/* select count(*) total_pv, count(submit_time) complete_pv, count(distinct if(submit_time is not null, exam_id, null)) complete_exam_cnt from exam_record; */
mysql> select count(*) total_pv,
-> count(submit_time) complete_pv,
-> count(distinct if(submit_time is not null, exam_id, null)) complete_exam_cnt
-> from exam_record;
+----------+-------------+-------------------+
| total_pv | complete_pv | complete_exam_cnt |
+----------+-------------+-------------------+
| 11 | 7 | 2 |
+----------+-------------+-------------------+
1 row in set (0.00 sec)
97、聚合函数的使用（3）
数据表：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），表中数据如下：
| 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) |
数据表：examination_info（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），表中数据如下：
| 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 |
【问题】请从试卷答题记录表中找到 SQL 试卷得分不小于该类试卷平均得分的用户最低得分。查询结果如下：
| min_score_over_avg |
|---|
| 87 |
表结构和数据如下：
/* drop table if exists examination_info; CREATE TABLE examination_info ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', exam_id int UNIQUE NOT NULL COMMENT '试卷ID', tag varchar(32) COMMENT '类别标签', difficulty varchar(8) COMMENT '难度', duration int NOT NULL COMMENT '时长', release_time datetime COMMENT '发布时间' )CHARACTER SET utf8 COLLATE utf8_general_ci; drop table if exists exam_record; CREATE TABLE exam_record ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', uid int NOT NULL COMMENT '用户ID', exam_id int NOT NULL COMMENT '试卷ID', start_time datetime NOT NULL COMMENT '开始时间', submit_time datetime COMMENT '提交时间', score tinyint COMMENT '得分' )CHARACTER SET utf8 COLLATE utf8_general_ci; INSERT INTO examination_info(exam_id,tag,difficulty,duration,release_time) VALUES (9001, 'SQL', 'hard', 60, '2020-01-01 10:00:00'), (9002, 'SQL', 'easy', 60, '2020-02-01 10:00:00'), (9003, '算法', 'medium', 80, '2020-08-02 10:00:00'); INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES (1001, 9001, '2020-01-02 09:01:01', '2020-01-02 09:21:01', 80), (1002, 9001, '2021-09-05 19:01:01', '2021-09-05 19:40:01', 89), (1002, 9002, '2021-09-02 12:01:01', null, null), (1002, 9003, '2021-09-01 12:01:01', null, null), (1002, 9001, '2021-02-02 19:01:01', '2021-02-02 19:30:01', 87), (1002, 9002, '2021-05-05 18:01:01', '2021-05-05 18:59:02', 90), (1003, 9002, '2021-02-06 12:01:01', null, null), (1003, 9003, '2021-09-07 10:01:01', '2021-09-07 10:31:01', 86), (1004, 9003, '2021-09-06 12:01:01', null, null); */
解答：
/* select min(score) min_score_over_avg from exam_record where exam_id in (select exam_id from examination_info where tag = 'SQL') and score >= (select avg(score) min_score_over_avg from exam_record where exam_id in (select exam_id from examination_info where tag = 'SQL')); */
mysql> select min(score) min_score_over_avg from exam_record where exam_id in
-> (select exam_id from examination_info where tag = 'SQL') and score >=
-> (select avg(score) min_score_over_avg from exam_record where exam_id in
-> (select exam_id from examination_info where tag = 'SQL'));
+--------------------+
| min_score_over_avg |
+--------------------+
| 87 |
+--------------------+
1 row in set (0.00 sec)
98、分组查询（1）
数据表：exam_record（uid：用户ID，exam_id：试卷ID，start_time：开始答题时间，submit_time：交卷时间，score：得分），表中数据如下：
| id | uid | exam_id | start_time | submit_time | score |
|---|---|---|---|---|---|
| 1 | 1001 | 9001 | 2021-07-02 09:01:01 | 2021-07-02 09:21:01 | 80 |
| 2 | 1002 | 9001 | 2021-09-05 19:01:01 | 2021-09-05 19:40:01 | 81 |
| 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 | 2021-07-02 19:01:01 | 2021-07-02 19:30:01 | 82 |
| 6 | 1002 | 9002 | 2021-07-05 18:01:01 | 2021-07-05 18:59:02 | 90 |
| 7 | 1003 | 9002 | 2021-07-06 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) |
| 10 | 1002 | 9003 | 2021-09-01 12:01:01 | 2021-09-01 12:31:01 | 81 |
| 11 | 1005 | 9001 | 2021-09-01 12:01:01 | 2021-09-01 12:31:01 | 88 |
| 12 | 1006 | 9002 | 2021-09-02 12:11:01 | 2021-09-02 12:31:01 | 89 |
| 13 | 1007 | 9002 | 2020-09-02 12:11:01 | 2020-09-02 12:31:01 | 89 |
【问题】请计算 2021 年每个月试卷答题用户的月度活跃天数 active_days 和月度活跃人数 mau。查询结果如下：
| month | active_days | mau |
|---|---|---|
| 202107 | 3 | 2 |
| 202109 | 5 | 4 |
表结构和数据如下：
/* drop table if exists exam_record; CREATE TABLE exam_record ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', uid int NOT NULL COMMENT '用户ID', exam_id int NOT NULL COMMENT '试卷ID', start_time datetime NOT NULL COMMENT '开始时间', submit_time datetime COMMENT '提交时间', score tinyint COMMENT '得分' )CHARACTER SET utf8 COLLATE utf8_general_ci; INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES (1001, 9001, '2021-07-02 09:01:01', '2021-07-02 09:21:01', 80), (1002, 9001, '2021-09-05 19:01:01', '2021-09-05 19:40:01', 81), (1002, 9002, '2021-09-02 12:01:01', null, null), (1002, 9003, '2021-09-01 12:01:01', null, null), (1002, 9001, '2021-07-02 19:01:01', '2021-07-02 19:30:01', 82), (1002, 9002, '2021-07-05 18:01:01', '2021-07-05 18:59:02', 90), (1003, 9002, '2021-07-06 12:01:01', null, null), (1003, 9003, '2021-09-07 10:01:01', '2021-09-07 10:31:01', 86), (1004, 9003, '2021-09-06 12:01:01', null, null), (1002, 9003, '2021-09-01 12:01:01', '2021-09-01 12:31:01', 81), (1005, 9001, '2021-09-01 12:01:01', '2021-09-01 12:31:01', 88), (1006, 9002, '2021-09-02 12:11:01', '2021-09-02 12:31:01', 89), (1007, 9002, '2020-09-02 12:11:01', '2020-09-02 12:31:01', 89); */
解答：
/* select concat(left(start_time,4), substr(start_time, 6, 2)) month, count(distinct uid) active_days, count(distinct date(submit_time)) mau from exam_record where year(start_time) = 2021 group by month; */
mysql> select concat(left(start_time,4), substr(start_time, 6, 2)) month,
-> count(distinct uid) active_days,
-> count(distinct date(submit_time)) mau
-> from exam_record
-> where year(start_time) = 2021
-> group by month;
+--------+-------------+-----+
| month | active_days | mau |
+--------+-------------+-----+
| 202107 | 3 | 2 |
| 202109 | 5 | 4 |
+--------+-------------+-----+
2 rows in set (0.00 sec)
99、分组查询（2）
数据表：practice_record，表中数据如下：
| id | uid | question_id | submit_time | score |
|---|---|---|---|---|
| 1 | 1001 | 8001 | 2021-08-02 11:41:01 | 60 |
| 2 | 1002 | 8001 | 2021-09-02 19:30:01 | 50 |
| 3 | 1002 | 8001 | 2021-09-02 19:20:01 | 70 |
| 4 | 1002 | 8002 | 2021-09-02 19:38:01 | 70 |
| 5 | 1003 | 8002 | 2021-08-01 19:38:01 | 80 |
【问题】请统计出 2021 年每个月用户的月总刷题数 month_q_cnt 和日均刷题数 avg_day_q_cnt（按月份升序排序）。查询结果如下：
| submit_month | month_q_cnt | avg_day_q_cnt |
|---|---|---|
| 202108 | 2 | 0.065 |
| 202109 | 3 | 0.100 |
表结构和数据如下：
/* drop table if exists practice_record; CREATE TABLE practice_record ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', uid int NOT NULL COMMENT '用户ID', question_id int NOT NULL COMMENT '题目ID', submit_time datetime COMMENT '提交时间', score tinyint COMMENT '得分' )CHARACTER SET utf8 COLLATE utf8_general_ci; INSERT INTO practice_record(uid,question_id,submit_time,score) VALUES (1001, 8001, '2021-08-02 11:41:01', 60), (1002, 8001, '2021-09-02 19:30:01', 50), (1002, 8001, '2021-09-02 19:20:01', 70), (1002, 8002, '2021-09-02 19:38:01', 70), (1003, 8002, '2021-08-01 19:38:01', 80); */
解答：
/* select submit_month, count(*) month_q_cnt, round(count(*)/day(last_day(concat(submit_month,'01'))),3) avg_day_q_cnt from (select *,concat(left(submit_time,4),substr(submit_time,6,2)) submit_month from practice_record where year(submit_time) = 2021) a group by submit_month order by submit_month; */
mysql> select submit_month,
-> count(*) month_q_cnt,
-> round(count(*)/day(last_day(concat(submit_month,'01'))),3) avg_day_q_cnt
-> from
-> (select *,concat(left(submit_time,4),substr(submit_time,6,2)) submit_month
-> from practice_record
-> where year(submit_time) = 2021) a
-> group by submit_month
-> order by submit_month;
+--------------+-------------+---------------+
| submit_month | month_q_cnt | avg_day_q_cnt |
+--------------+-------------+---------------+
| 202108 | 2 | 0.065 |
| 202109 | 3 | 0.100 |
+--------------+-------------+---------------+
2 rows in set (0.00 sec)
100、分组查询（3）
数据表：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），表中数据如下：
| id | uid | exam_id | start_time | submit_time | score |
|---|---|---|---|---|---|
| 1 | 1001 | 9001 | 2021-07-02 09:01:01 | 2021-07-02 09:21:01 | 80 |
| 2 | 1002 | 9001 | 2021-09-05 19:01:01 | 2021-09-05 19:40:01 | 81 |
| 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 | 2021-07-02 19:01:01 | 2021-07-02 19:30:01 | 82 |
| 6 | 1002 | 9002 | 2021-07-05 18:01:01 | 2021-07-05 18:59:02 | 90 |
| 7 | 1003 | 9002 | 2021-07-06 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) |
| 10 | 1002 | 9003 | 2021-09-01 12:01:01 | 2021-09-01 12:31:01 | 81 |
| 11 | 1005 | 9001 | 2021-09-01 12:01:01 | 2021-09-01 12:31:01 | 88 |
| 12 | 1005 | 9002 | 2021-09-01 12:01:01 | 2021-09-01 12:31:01 | 88 |
| 13 | 1006 | 9002 | 2021-09-02 12:11:01 | 2021-09-02 12:31:01 | 89 |
试卷信息表：examination_info（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），表中数据如下：
| 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 |
【问题】统计 2021 年每个未完成试卷作答数大于 1 的有效用户的数据（有效用户指完成试卷作答数至少为 1 且未完成数小于5），输出用户ID、未完成试卷作答数、完成试卷作答数、作答过的试卷 tag 集合，按未完成试卷数量由多到少排序。查询结果如下：
| uid | incomplete_cnt | complete_cnt | detail |
|---|---|---|---|
| 1002 | 2 | 4 | 2021-09-01:算法;2021-07-02:SQL;2021-09-02:SQL;2021-09-05:SQL;2021-07-05:SQL |
表结构和数据如下：
/* drop table if exists examination_info; CREATE TABLE examination_info ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', exam_id int UNIQUE NOT NULL COMMENT '试卷ID', tag varchar(32) COMMENT '类别标签', difficulty varchar(8) COMMENT '难度', duration int NOT NULL COMMENT '时长', release_time datetime COMMENT '发布时间' )CHARACTER SET utf8 COLLATE utf8_general_ci; drop table if exists exam_record; CREATE TABLE exam_record ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', uid int NOT NULL COMMENT '用户ID', exam_id int NOT NULL COMMENT '试卷ID', start_time datetime NOT NULL COMMENT '开始时间', submit_time datetime COMMENT '提交时间', score tinyint COMMENT '得分' )CHARACTER SET utf8 COLLATE utf8_general_ci; INSERT INTO examination_info(exam_id,tag,difficulty,duration,release_time) VALUES (9001, 'SQL', 'hard', 60, '2020-01-01 10:00:00'), (9002, 'SQL', 'easy', 60, '2020-02-01 10:00:00'), (9003, '算法', 'medium', 80, '2020-08-02 10:00:00'); INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES (1001, 9001, '2021-07-02 09:01:01', '2021-07-02 09:21:01', 80), (1002, 9001, '2021-09-05 19:01:01', '2021-09-05 19:40:01', 81), (1002, 9002, '2021-09-02 12:01:01', null, null), (1002, 9003, '2021-09-01 12:01:01', null, null), (1002, 9001, '2021-07-02 19:01:01', '2021-07-02 19:30:01', 82), (1002, 9002, '2021-07-05 18:01:01', '2021-07-05 18:59:02', 90), (1003, 9002, '2021-07-06 12:01:01', null, null), (1003, 9003, '2021-09-07 10:01:01', '2021-09-07 10:31:01', 86), (1004, 9003, '2021-09-06 12:01:01', null, null), (1002, 9003, '2021-09-01 12:01:01', '2021-09-01 12:31:01', 81), (1005, 9001, '2021-09-01 12:01:01', '2021-09-01 12:31:01', 88), (1005, 9002, '2021-09-01 12:01:01', '2021-09-01 12:31:01', 88), (1006, 9002, '2021-09-02 12:11:01', '2021-09-02 12:31:01', 89); */
解答：
/* select e.uid, sum(if(e.submit_time is null, 1, 0)) incomplete_cnt, sum(if(e.submit_time is null, 0, 1))complete_cnt, group_concat(concat(date(e.submit_time),':',if(e.submit_time is null, null, i.tag)) separator ';') detail from exam_record e join examination_info i on e.exam_id = i.exam_id where year(start_time) = 2021 group by e.uid having incomplete_cnt > 1 and incomplete_cnt < 5; */
mysql> select e.uid,
-> sum(if(e.submit_time is null, 1, 0)) incomplete_cnt,
-> sum(if(e.submit_time is null, 0, 1))complete_cnt,
-> group_concat(concat(date(e.submit_time),':',if(e.submit_time is null, null, i.tag)) separator ';') detail
-> from exam_record e join examination_info i on e.exam_id = i.exam_id
-> where year(start_time) = 2021
-> group by e.uid
-> having incomplete_cnt > 1 and incomplete_cnt < 5;
+------+----------------+--------------+--------------------------------------------------------+
| uid | incomplete_cnt | complete_cnt | detail |
+------+----------------+--------------+--------------------------------------------------------+
| 1002 | 2 | 4 | 2021-07-02:SQL;2021-09-05:SQL;2021-07-05:SQL;2021-09-01:算法 |
+------+----------------+--------------+--------------------------------------------------------+
1 row in set (0.00 sec)
边栏推荐
- matlab simulink锂离子电池智能充电策略研究
- torch.optim.Adam() function usage
- 图卷积神经网络的数学原理——谱图理论和傅里叶变换初探
- Error EPERM operation not permitted, mkdir ‘Dsoftwarenodejsnode_cache_cacach两种解决办法
- 说几个大厂分库分表的那点破事。
- Valid bracketed strings [greedy exercise]
- 592. Fraction Addition and Subtraction
- 华为云数据治理生产线DataArts，让“数据‘慧’说话”
- 简易的命令行入门教程
- Prometheus 基本概念
猜你喜欢
![[HarekazeCTF2019] Avatar Uploader 1](/img/2c/6dde7b8d34ba0deb334b4283e1e30e.png)
随机推荐
【Cloud Store Announcement】Notice of Help Center Update on July 30
Error occurred while trying to proxy request The project suddenly can't get up
字符串复制、拼接、比较以及分割函数总结（一）
你是这样的volatile，出乎意料
【云商店公告】关于7月30日帮助中心更新通知
基于stm32的shell实现
游戏化产品搭建思路的拆解与探究
华为无线设备Mesh配置命令
Weka 3.8.6安装与Weka 3.8.6功能介绍
论文阅读之《DeepIlluminance: Contextual IlluminanceEstimation via Deep Neural Networks》
C语言向MySQL插入数据
C陷阱与缺陷 第7章 可移植性缺陷 7.4 字符是有符号数还是无符号数
Shell implementation based on stm32
17.机器学习系统的设计
腾讯专家献上技术干货，带你一览腾讯广告召回系统的演进
实现web实时消息推送的7种方案
Go新项目-编译热加载使用和对比，让开发更自由（3）
Oracle动态监听与静态监听详解
.NET 6.0中使用Identity框架实现JWT身份认证与授权
Error occurred while trying to proxy request项目突然起不来了