hellodb_MyISAM 练习题目 mariadb的select查询练习
准备阶段
1.将 hellodb_innodb.sql 导入到 数据库中
[root@centos7K data]#mysql -u root -pcentos < hellodb_innodb.sql
[root@centos7K data]#mysql -u root -pcentos
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 17
Server version: 10.2.29-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]> show dataabases;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB
server version for the right syntax to use near 'dataabases' at line 1
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| hellodb |
| information_schema |
| mysql |
| performance_schema |
| school |
+--------------------+
5 rows in set (0.00 sec)
MariaDB [(none)]>
MariaDB [(none)]> use hellodb
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [hellodb]>
第一部分
第1题
在 students 表中，查询年龄大于25岁，且为男性的同学的名字和年龄:
MariaDB [hellodb]> show databases;
+--------------------+
| Database |
+--------------------+
| hellodb |
| information_schema |
| mysql |
| performance_schema |
| school |
+--------------------+
MariaDB [hellodb]> show tables;
+-------------------+
| Tables_in_hellodb |
+-------------------+
| classes |
| coc |
| courses |
| scores |
| students |
| teachers |
| toc |
+-------------------+
7 rows in set (0.00 sec)
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.01 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select name,age from students where gender="M" and age>25;
+--------------+-----+
| name | age |
+--------------+-----+
| Xie Yanke | 53 |
| Ding Dian | 32 |
| Yu Yutong | 26 |
| Shi Qing | 46 |
| Tian Boguang | 33 |
| Xu Xian | 27 |
| Sun Dasheng | 100 |
+--------------+-----+
7 rows in set (0.00 sec)
MariaDB [hellodb]>
第2题
在 students 表中，以 ClassID 为分组依据，查询显示每组的平均年龄
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.01 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select classid,avg(age) as avg_age from students group by classid;
+---------+---------+
| classid | avg_age |
+---------+---------+
| NULL | 63.5000 |
| 1 | 20.5000 |
| 2 | 36.0000 |
| 3 | 20.2500 |
| 4 | 24.7500 |
| 5 | 46.0000 |
| 6 | 20.7500 |
| 7 | 19.6667 |
+---------+---------+
8 rows in set (0.01 sec)
第3题
显示第2题中平均年龄大于30的分组及平均年龄
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select classid,avg(age) as avg_age from students group by classid having avg_age > 30;
+---------+---------+
| classid | avg_age |
+---------+---------+
| NULL | 63.5000 |
| 2 | 36.0000 |
| 5 | 46.0000 |
+---------+---------+
3 rows in set (0.00 sec)
第4题
显示以L开头的名字的同学的信息
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students where name like "L%";
+-------+-------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+-------------+-----+--------+---------+-----------+
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
+-------+-------------+-----+--------+---------+-----------+
3 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students where name rlike "^L.*";
+-------+-------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+-------------+-----+--------+---------+-----------+
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
+-------+-------------+-----+--------+---------+-----------+
3 rows in set (0.01 sec)
MariaDB [hellodb]> select * from students where name regexp "^L.*";
+-------+-------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+-------------+-----+--------+---------+-----------+
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
+-------+-------------+-----+--------+---------+-----------+
3 rows in set (0.00 sec)
第5题
显示TeacherID非空的同学的相关信息
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students where teacherid is not null;
+-------+-------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+-------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
+-------+-------------+-----+--------+---------+-----------+
5 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students where teacherid rlike "[0-9]+";
+-------+-------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+-------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
+-------+-------------+-----+--------+---------+-----------+
5 rows in set (0.00 sec)
第6题
students 表中，查询以年龄排序后的数据，并且显示年龄最大的前10位同学的信息
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students order by age desc limit 10;
+-------+--------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+--------------+-----+--------+---------+-----------+
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
+-------+--------------+-----+--------+---------+-----------+
10 rows in set (0.00 sec)
desc是从大到小 默认是从小到大。 limit 是限制取出
第7题
students 表中，查询年龄大于等于20岁，小于等于25岁的同学的信息
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students where age>=20 and age<=25;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
+-------+---------------+-----+--------+---------+-----------+
10 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students where age between 20 and 25;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
+-------+---------------+-----+--------+---------+-----------+
10 rows in set (0.00 sec)
between ...on...语法只能在等于的时候能用。
MariaDB [hellodb]> select * from students where age in (20,21,22,23,24,25);
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
+-------+---------------+-----+--------+---------+-----------+
10 rows in set (0.00 sec)
in （a,b,c...） 适用于比较少，或者特定的列
第二部分
第1题
以ClassID分组，显示每班的同学的人数
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select classid,count(*) as stud_num from students group by classid;
+---------+----------+
| classid | stud_num |
+---------+----------+
| NULL | 2 |
| 1 | 4 |
| 2 | 3 |
| 3 | 4 |
| 4 | 4 |
| 5 | 1 |
| 6 | 4 |
| 7 | 3 |
+---------+----------+
8 rows in set (0.00 sec)
第2题
以Gender分组，显示其年龄之和
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select gender,sum(age) as tatol_age from students group by gender;
+--------+-----------+
| gender | tatol_age |
+--------+-----------+
| F | 190 |
| M | 495 |
+--------+-----------+
2 rows in set (0.00 sec)
第3题
以ClassID分组，显示其平均年龄大于25的班级
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select classid,avg(age) as avg_age from students group by classid;
+---------+---------+
| classid | avg_age |
+---------+---------+
| NULL | 63.5000 |
| 1 | 20.5000 |
| 2 | 36.0000 |
| 3 | 20.2500 |
| 4 | 24.7500 |
| 5 | 46.0000 |
| 6 | 20.7500 |
| 7 | 19.6667 |
+---------+---------+
MariaDB [hellodb]> select classid,avg(age) as avg_age from students group by classid having avg_age > 25;
+---------+---------+
| classid | avg_age |
+---------+---------+
| NULL | 63.5000 |
| 2 | 36.0000 |
| 5 | 46.0000 |
+---------+---------+
3 rows in set (0.00 sec)
第4题
以Gender分组，显示各组中年龄大于18的学员的年龄之和
MariaDB [hellodb]> desc students;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| StuID | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(50) | NO | | NULL | |
| Age | tinyint(3) unsigned | NO | | NULL | |
| Gender | enum('F','M') | NO | | NULL | |
| ClassID | tinyint(3) unsigned | YES | | NULL | |
| TeacherID | int(10) unsigned | YES | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students where age > 18;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
22 rows in set (0.00 sec)
MariaDB [hellodb]> select gender,sum(age) as sum_age from students where age > 18 group by gender;
+--------+---------+
| gender | sum_age |
+--------+---------+
| F | 138 |
| M | 495 |
+--------+---------+
2 rows in set (0.00 sec)
第三部分
第5题
显示前5位同学的姓名、课程及成绩
MariaDB [hellodb]> show databases;
+--------------------+
| Database |
+--------------------+
| hellodb |
| information_schema |
| mysql |
| performance_schema |
| school |
+--------------------+
5 rows in set (0.00 sec)
MariaDB [hellodb]> show tables;
+-------------------+
| Tables_in_hellodb |
+-------------------+
| classes |
| coc |
| courses |
| scores |
| students |
| teachers |
| toc |
+-------------------+
7 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select * from classes;
+---------+----------------+----------+
| ClassID | Class | NumOfStu |
+---------+----------------+----------+
| 1 | Shaolin Pai | 10 |
| 2 | Emei Pai | 7 |
| 3 | QingCheng Pai | 11 |
| 4 | Wudang Pai | 12 |
| 5 | Riyue Shenjiao | 31 |
| 6 | Lianshan Pai | 27 |
| 7 | Ming Jiao | 27 |
| 8 | Xiaoyao Pai | 15 |
+---------+----------------+----------+
8 rows in set (0.00 sec)
MariaDB [hellodb]> select * from courses;
+----------+----------------+
| CourseID | Course |
+----------+----------------+
| 1 | Hamo Gong |
| 2 | Kuihua Baodian |
| 3 | Jinshe Jianfa |
| 4 | Taiji Quan |
| 5 | Daiyu Zanghua |
| 6 | Weituo Zhang |
| 7 | Dagou Bangfa |
+----------+----------------+
7 rows in set (0.00 sec)
MariaDB [hellodb]> select stu.StuID,stu.Name,co.Course,sc.Score from students as stu inner join scores as
sc on stu.StuID = sc.StuID inner join courses as co on sc.CourseID = co.CourseID;
+-------+-------------+----------------+-------+
| StuID | Name | Course | Score |
+-------+-------------+----------------+-------+
| 1 | Shi Zhongyu | Kuihua Baodian | 77 |
| 1 | Shi Zhongyu | Weituo Zhang | 93 |
| 2 | Shi Potian | Kuihua Baodian | 47 |
| 2 | Shi Potian | Daiyu Zanghua | 97 |
| 3 | Xie Yanke | Kuihua Baodian | 88 |
| 3 | Xie Yanke | Weituo Zhang | 75 |
| 4 | Ding Dian | Daiyu Zanghua | 71 |
| 4 | Ding Dian | Kuihua Baodian | 89 |
| 5 | Yu Yutong | Hamo Gong | 39 |
| 5 | Yu Yutong | Dagou Bangfa | 63 |
| 6 | Shi Qing | Hamo Gong | 96 |
| 7 | Xi Ren | Hamo Gong | 86 |
| 7 | Xi Ren | Dagou Bangfa | 83 |
| 8 | Lin Daiyu | Taiji Quan | 57 |
| 8 | Lin Daiyu | Jinshe Jianfa | 93 |
+-------+-------------+----------------+-------+
15 rows in set (0.00 sec)
MariaDB [hellodb]> select stu.StuID,stu.Name,co.Course,sc.Score from students as stu inner join scores as
sc on stu.StuID = sc.StuID inner join courses as co on sc.CourseID = co.CourseID where stu.StuID <= 5;
+-------+-------------+----------------+-------+
| StuID | Name | Course | Score |
+-------+-------------+----------------+-------+
| 1 | Shi Zhongyu | Kuihua Baodian | 77 |
| 1 | Shi Zhongyu | Weituo Zhang | 93 |
| 2 | Shi Potian | Kuihua Baodian | 47 |
| 2 | Shi Potian | Daiyu Zanghua | 97 |
| 3 | Xie Yanke | Kuihua Baodian | 88 |
| 3 | Xie Yanke | Weituo Zhang | 75 |
| 4 | Ding Dian | Daiyu Zanghua | 71 |
| 4 | Ding Dian | Kuihua Baodian | 89 |
| 5 | Yu Yutong | Hamo Gong | 39 |
| 5 | Yu Yutong | Dagou Bangfa | 63 |
+-------+-------------+----------------+-------+
10 rows in set (0.00 sec)
第6题
显示其成绩高于80的同学的名称及课程
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select * from classes;
+---------+----------------+----------+
| ClassID | Class | NumOfStu |
+---------+----------------+----------+
| 1 | Shaolin Pai | 10 |
| 2 | Emei Pai | 7 |
| 3 | QingCheng Pai | 11 |
| 4 | Wudang Pai | 12 |
| 5 | Riyue Shenjiao | 31 |
| 6 | Lianshan Pai | 27 |
| 7 | Ming Jiao | 27 |
| 8 | Xiaoyao Pai | 15 |
+---------+----------------+----------+
8 rows in set (0.00 sec)
MariaDB [hellodb]> select * from scores;
+----+-------+----------+-------+
| ID | StuID | CourseID | Score |
+----+-------+----------+-------+
| 1 | 1 | 2 | 77 |
| 2 | 1 | 6 | 93 |
| 3 | 2 | 2 | 47 |
| 4 | 2 | 5 | 97 |
| 5 | 3 | 2 | 88 |
| 6 | 3 | 6 | 75 |
| 7 | 4 | 5 | 71 |
| 8 | 4 | 2 | 89 |
| 9 | 5 | 1 | 39 |
| 10 | 5 | 7 | 63 |
| 11 | 6 | 1 | 96 |
| 12 | 7 | 1 | 86 |
| 13 | 7 | 7 | 83 |
| 14 | 8 | 4 | 57 |
| 15 | 8 | 3 | 93 |
+----+-------+----------+-------+
15 rows in set (0.00 sec)
MariaDB [hellodb]> select students.StuID,students.Name,classes.Class,scores.Score from students inner
join classes on students.ClassID = classes.ClassID inner join scores on students.StuID = scores.StuID
where scores.Score >=80;
+-------+-------------+----------------+-------+
| StuID | Name | Class | Score |
+-------+-------------+----------------+-------+
| 1 | Shi Zhongyu | Emei Pai | 93 |
| 2 | Shi Potian | Shaolin Pai | 97 |
| 3 | Xie Yanke | Emei Pai | 88 |
| 4 | Ding Dian | Wudang Pai | 89 |
| 6 | Shi Qing | Riyue Shenjiao | 96 |
| 7 | Xi Ren | QingCheng Pai | 86 |
| 7 | Xi Ren | QingCheng Pai | 83 |
| 8 | Lin Daiyu | Ming Jiao | 93 |
+-------+-------------+----------------+-------+
8 rows in set (0.00 sec)
第7题
取每位同学各门课的平均成绩，显示成绩前三名的同学的姓名和平均成绩
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select * from classes;
+---------+----------------+----------+
| ClassID | Class | NumOfStu |
+---------+----------------+----------+
| 1 | Shaolin Pai | 10 |
| 2 | Emei Pai | 7 |
| 3 | QingCheng Pai | 11 |
| 4 | Wudang Pai | 12 |
| 5 | Riyue Shenjiao | 31 |
| 6 | Lianshan Pai | 27 |
| 7 | Ming Jiao | 27 |
| 8 | Xiaoyao Pai | 15 |
+---------+----------------+----------+
8 rows in set (0.00 sec)
MariaDB [hellodb]> select * from scores;
+----+-------+----------+-------+
| ID | StuID | CourseID | Score |
+----+-------+----------+-------+
| 1 | 1 | 2 | 77 |
| 2 | 1 | 6 | 93 |
| 3 | 2 | 2 | 47 |
| 4 | 2 | 5 | 97 |
| 5 | 3 | 2 | 88 |
| 6 | 3 | 6 | 75 |
| 7 | 4 | 5 | 71 |
| 8 | 4 | 2 | 89 |
| 9 | 5 | 1 | 39 |
| 10 | 5 | 7 | 63 |
| 11 | 6 | 1 | 96 |
| 12 | 7 | 1 | 86 |
| 13 | 7 | 7 | 83 |
| 14 | 8 | 4 | 57 |
| 15 | 8 | 3 | 93 |
+----+-------+----------+-------+
15 rows in set (0.00 sec)
MariaDB [hellodb]> select student.Name,avg(student.Score) as newsc from (select students.StuID,students.Name,
scores.Score from students inner join scores on students.StuID = scores.StuID)
as student group by student.Name;
+-------------+---------+
| Name | newsc |
+-------------+---------+
| Ding Dian | 80.0000 |
| Lin Daiyu | 75.0000 |
| Shi Potian | 72.0000 |
| Shi Qing | 96.0000 |
| Shi Zhongyu | 85.0000 |
| Xi Ren | 84.5000 |
| Xie Yanke | 81.5000 |
| Yu Yutong | 51.0000 |
+-------------+---------+
8 rows in set (0.00 sec)
MariaDB [hellodb]> select student.Name,avg(student.Score) as newsc from (select students.StuID,students.Name,
scores.Score from students inner join scores on students.StuID = scores.StuID)
as student group by student.Name order by newsc desc;
+-------------+---------+
| Name | newsc |
+-------------+---------+
| Shi Qing | 96.0000 |
| Shi Zhongyu | 85.0000 |
| Xi Ren | 84.5000 |
| Xie Yanke | 81.5000 |
| Ding Dian | 80.0000 |
| Lin Daiyu | 75.0000 |
| Shi Potian | 72.0000 |
| Yu Yutong | 51.0000 |
+-------------+---------+
8 rows in set (0.00 sec)
MariaDB [hellodb]> select student.Name,avg(student.Score) as newsc from (select students.
StuID,students.Name,scores.Score from students inner join scores on students.StuID = scores.StuID)
as student group by student.Name order by newsc desc limit 3;
+-------------+---------+
| Name | newsc |
+-------------+---------+
| Shi Qing | 96.0000 |
| Shi Zhongyu | 85.0000 |
| Xi Ren | 84.5000 |
+-------------+---------+
3 rows in set (0.00 sec)
第8题
显示每门课程课程名称及学习了这门课的同学的个数
MariaDB [hellodb]> select * from courses;
+----------+----------------+
| CourseID | Course |
+----------+----------------+
| 1 | Hamo Gong |
| 2 | Kuihua Baodian |
| 3 | Jinshe Jianfa |
| 4 | Taiji Quan |
| 5 | Daiyu Zanghua |
| 6 | Weituo Zhang |
| 7 | Dagou Bangfa |
+----------+----------------+
7 rows in set (0.00 sec)
MariaDB [hellodb]> select * from scores;
+----+-------+----------+-------+
| ID | StuID | CourseID | Score |
+----+-------+----------+-------+
| 1 | 1 | 2 | 77 |
| 2 | 1 | 6 | 93 |
| 3 | 2 | 2 | 47 |
| 4 | 2 | 5 | 97 |
| 5 | 3 | 2 | 88 |
| 6 | 3 | 6 | 75 |
| 7 | 4 | 5 | 71 |
| 8 | 4 | 2 | 89 |
| 9 | 5 | 1 | 39 |
| 10 | 5 | 7 | 63 |
| 11 | 6 | 1 | 96 |
| 12 | 7 | 1 | 86 |
| 13 | 7 | 7 | 83 |
| 14 | 8 | 4 | 57 |
| 15 | 8 | 3 | 93 |
+----+-------+----------+-------+
15 rows in set (0.00 sec)
MariaDB [hellodb]> select co.CourseID,co.Course,sc.num from courses as co inner join (select CourseID,count(*)
as num from scores group by CourseID) as sc on sc.CourseID = co.CourseID;
+----------+----------------+-----+
| CourseID | Course | num |
+----------+----------------+-----+
| 1 | Hamo Gong | 3 |
| 2 | Kuihua Baodian | 4 |
| 3 | Jinshe Jianfa | 1 |
| 4 | Taiji Quan | 1 |
| 5 | Daiyu Zanghua | 2 |
| 6 | Weituo Zhang | 2 |
| 7 | Dagou Bangfa | 2 |
+----------+----------------+-----+
7 rows in set (0.00 sec)
MariaDB [hellodb]> select co.CourseID,co.Course,count(sc.StuID) as num from courses co left join scores as
sc on co.CourseID = sc.CourseID group by co.Course order by CourseID;
+----------+----------------+-----+
| CourseID | Course | num |
+----------+----------------+-----+
| 1 | Hamo Gong | 3 |
| 2 | Kuihua Baodian | 4 |
| 3 | Jinshe Jianfa | 1 |
| 4 | Taiji Quan | 1 |
| 5 | Daiyu Zanghua | 2 |
| 6 | Weituo Zhang | 2 |
| 7 | Dagou Bangfa | 2 |
+----------+----------------+-----+
7 rows in set (0.00 sec)
第9题
显示其年龄大于平均年龄的同学的名字
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select Name,Age from students where Age > (select avg(Age) from students);
+--------------+-----+
| Name | Age |
+--------------+-----+
| Xie Yanke | 53 |
| Ding Dian | 32 |
| Shi Qing | 46 |
| Tian Boguang | 33 |
| Sun Dasheng | 100 |
+--------------+-----+
5 rows in set (0.00 sec)
第10题
显示其学习的课程为第1或第7门课的同学的名字
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]>
MariaDB [hellodb]> select * from scores;
+----+-------+----------+-------+
| ID | StuID | CourseID | Score |
+----+-------+----------+-------+
| 1 | 1 | 2 | 77 |
| 2 | 1 | 6 | 93 |
| 3 | 2 | 2 | 47 |
| 4 | 2 | 5 | 97 |
| 5 | 3 | 2 | 88 |
| 6 | 3 | 6 | 75 |
| 7 | 4 | 5 | 71 |
| 8 | 4 | 2 | 89 |
| 9 | 5 | 1 | 39 |
| 10 | 5 | 7 | 63 |
| 11 | 6 | 1 | 96 |
| 12 | 7 | 1 | 86 |
| 13 | 7 | 7 | 83 |
| 14 | 8 | 4 | 57 |
| 15 | 8 | 3 | 93 |
+----+-------+----------+-------+
15 rows in set (0.00 sec)
MariaDB [hellodb]> select StuID,Name from students where StuID in (select distinct StuID from scores where
CourseID in (1,7));
+-------+-----------+
| StuID | Name |
+-------+-----------+
| 5 | Yu Yutong |
| 6 | Shi Qing |
| 7 | Xi Ren |
+-------+-----------+
3 rows in set (0.00 sec)
第11题 —1
显示其成员数最少 的 3个的班级的同学中年龄大于同班同学平均年龄的同学
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select ClassID,count(*) as num from students group by ClassID having ClassID is not null
order by num ;
+---------+-----+
| ClassID | num |
+---------+-----+
| 5 | 1 |
| 2 | 3 |
| 7 | 3 |
| 1 | 4 |
| 4 | 4 |
| 3 | 4 |
| 6 | 4 |
+---------+-----+
7 rows in set (0.00 sec)
MariaDB [hellodb]> select ClassID,count(*) as num from students group by ClassID having ClassID is not null
order by num limit 3;
+---------+-----+
| ClassID | num |
+---------+-----+
| 5 | 1 |
| 2 | 3 |
| 7 | 3 |
+---------+-----+
3 rows in set (0.00 sec)
MariaDB [hellodb]>
MariaDB [hellodb]> select * from students inner join (select ClassID,count(*) as num from students group by
ClassID having ClassID is not null order by num limit 3) as min_ClassID on students.ClassID = min_ClassID.ClassID;
+-------+--------------+-----+--------+---------+-----------+---------+-----+
| StuID | Name | Age | Gender | ClassID | TeacherID | ClassID | num |
+-------+--------------+-----+--------+---------+-----------+---------+-----+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 | 2 | 3 |
| 3 | Xie Yanke | 53 | M | 2 | 16 | 2 | 3 |
| 6 | Shi Qing | 46 | M | 5 | NULL | 5 | 1 |
| 8 | Lin Daiyu | 17 | F | 7 | NULL | 7 | 3 |
| 13 | Tian Boguang | 33 | M | 2 | NULL | 2 | 3 |
| 18 | Hua Rong | 23 | M | 7 | NULL | 7 | 3 |
| 20 | Diao Chan | 19 | F | 7 | NULL | 7 | 3 |
+-------+--------------+-----+--------+---------+-----------+---------+-----+
优化一下：
MariaDB [hellodb]> select students.StuID,students.Name,students.Age,students.ClassID,min_ClassID.ClassID,min_ClassID.num
from students inner join (select ClassID,count(*) as num from students group by ClassID having
ClassID is not null order by num limit 3) as min_ClassID on students.ClassID = min_ClassID.ClassID;
+-------+--------------+-----+---------+---------+-----+
| StuID | Name | Age | ClassID | ClassID | num |
+-------+--------------+-----+---------+---------+-----+
| 1 | Shi Zhongyu | 22 | 2 | 2 | 3 |
| 3 | Xie Yanke | 53 | 2 | 2 | 3 |
| 6 | Shi Qing | 46 | 5 | 5 | 1 |
| 8 | Lin Daiyu | 17 | 7 | 7 | 3 |
| 13 | Tian Boguang | 33 | 2 | 2 | 3 |
| 18 | Hua Rong | 23 | 7 | 7 | 3 |
| 20 | Diao Chan | 19 | 7 | 7 | 3 |
+-------+--------------+-----+---------+---------+-----+
7 rows in set (0.00 sec)
MariaDB [hellodb]> select stu.ClassID, avg(stu.Age) from students as stu inner join (select ClassID, count(*)
as num from students group by ClassID having ClassID is not null order by num limit 3) as min_ClassID on
stu.ClassID = min_ClassID.ClassID group by stu.ClassID;
+---------+--------------+
| ClassID | avg(stu.Age) |
+---------+--------------+
| 2 | 36.0000 |
| 5 | 46.0000 |
| 7 | 19.6667 |
+---------+--------------+
3 rows in set (0.00 sec)
MariaDB [hellodb]>
MariaDB [hellodb]> select * from students inner join (select stu.ClassID, avg(stu.Age) as avgAge from
students as stu inner join (select ClassID, count(*) as num from students group by ClassID having ClassID is
not null order by num limit 3) as min_ClassID on stu.ClassID = min_ClassID.ClassID group by stu.ClassID) as
avgtab on students.ClassID = avgtab.ClassID and students.age > avgtab.avgAge;
+-------+-----------+-----+--------+---------+-----------+---------+---------+
| StuID | Name | Age | Gender | ClassID | TeacherID | ClassID | avgAge |
+-------+-----------+-----+--------+---------+-----------+---------+---------+
| 3 | Xie Yanke | 53 | M | 2 | 16 | 2 | 36.0000 |
| 18 | Hua Rong | 23 | M | 7 | NULL | 7 | 19.6667 |
+-------+-----------+-----+--------+---------+-----------+---------+---------+
2 rows in set (0.00 sec)
第11题 —2
显示其成员数最少 为 3个的班级的同学中年龄大于同班同学平均年龄的同学
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select ClassID,count(*) as num from students group by ClassID having ClassID is not null
and num >=3 ;
+---------+-----+
| ClassID | num |
+---------+-----+
| 1 | 4 |
| 2 | 3 |
| 3 | 4 |
| 4 | 4 |
| 6 | 4 |
| 7 | 3 |
+---------+-----+
6 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students as stu inner join ( select ClassID, count(*) as num from students
group by ClassID having ClassID is not null and num >= 3 ) as sclass on stu.ClassID = sclass.ClassID;
+-------+---------------+-----+--------+---------+-----------+---------+-----+
| StuID | Name | Age | Gender | ClassID | TeacherID | ClassID | num |
+-------+---------------+-----+--------+---------+-----------+---------+-----+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 | 1 | 4 |
| 3 | Xie Yanke | 53 | M | 2 | 16 | 2 | 3 |
| 4 | Ding Dian | 32 | M | 4 | 4 | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 | 3 | 4 |
| 7 | Xi Ren | 19 | F | 3 | NULL | 3 | 4 |
| 8 | Lin Daiyu | 17 | F | 7 | NULL | 7 | 3 |
| 9 | Ren Yingying | 20 | F | 6 | NULL | 6 | 4 |
| 10 | Yue Lingshan | 19 | F | 3 | NULL | 3 | 4 |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL | 6 | 4 |
| 12 | Wen Qingqing | 19 | F | 1 | NULL | 1 | 4 |
| 13 | Tian Boguang | 33 | M | 2 | NULL | 2 | 3 |
| 14 | Lu Wushuang | 17 | F | 3 | NULL | 3 | 4 |
| 15 | Duan Yu | 19 | M | 4 | NULL | 4 | 4 |
| 16 | Xu Zhu | 21 | M | 1 | NULL | 1 | 4 |
| 17 | Lin Chong | 25 | M | 4 | NULL | 4 | 4 |
| 18 | Hua Rong | 23 | M | 7 | NULL | 7 | 3 |
| 19 | Xue Baochai | 18 | F | 6 | NULL | 6 | 4 |
| 20 | Diao Chan | 19 | F | 7 | NULL | 7 | 3 |
| 21 | Huang Yueying | 22 | F | 6 | NULL | 6 | 4 |
| 22 | Xiao Qiao | 20 | F | 1 | NULL | 1 | 4 |
| 23 | Ma Chao | 23 | M | 4 | NULL | 4 | 4 |
+-------+---------------+-----+--------+---------+-----------+---------+-----+
22 rows in set (0.00 sec)
MariaDB [hellodb]>
MariaDB [hellodb]> select * from students inner join (select stu.ClassID, avg(stu.Age) as avgAge from students
as stu inner join (select ClassID, count(*) as num from students group by ClassID having ClassID is not null
and num >= 3) as sclass on stu.ClassID = sclass.ClassID group by stu.ClassID) as avgtab on students.ClassID
= avgtab.ClassID and students.age > avgtab.avgAge;
+-------+---------------+-----+--------+---------+-----------+---------+---------+
| StuID | Name | Age | Gender | ClassID | TeacherID | ClassID | avgAge |
+-------+---------------+-----+--------+---------+-----------+---------+---------+
| 2 | Shi Potian | 22 | M | 1 | 7 | 1 | 20.5000 |
| 3 | Xie Yanke | 53 | M | 2 | 16 | 2 | 36.0000 |
| 4 | Ding Dian | 32 | M | 4 | 4 | 4 | 24.7500 |
| 5 | Yu Yutong | 26 | M | 3 | 1 | 3 | 20.2500 |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL | 6 | 20.7500 |
| 16 | Xu Zhu | 21 | M | 1 | NULL | 1 | 20.5000 |
| 17 | Lin Chong | 25 | M | 4 | NULL | 4 | 24.7500 |
| 18 | Hua Rong | 23 | M | 7 | NULL | 7 | 19.6667 |
| 21 | Huang Yueying | 22 | F | 6 | NULL | 6 | 20.7500 |
+-------+---------------+-----+--------+---------+-----------+---------+---------+
9 rows in set (0.00 sec)
第12题
统计各班级中年龄大于全校同学平均年龄的同学
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)
MariaDB [hellodb]> select avg(Age) from students where ClassID is not null;
+----------+
| avg(Age) |
+----------+
| 24.2609 |
+----------+
1 row in set (0.00 sec)
select * from students where Age > (select avg(Age) from students where ClassI' at line 1
MariaDB [hellodb]> select * from students where Age > (select avg(Age) from students where ClassID is not
null);
+-------+--------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+--------------+-----+--------+---------+-----------+
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+--------------+-----+--------+---------+-----------+
8 rows in set (0.00 sec)
MariaDB [hellodb]> select * from students where Age > (select avg(Age) from students where ClassID is not
null) and ClassID is not null;
+-------+--------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+--------------+-----+--------+---------+-----------+
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
+-------+--------------+-----+--------+---------+-----------+
6 rows in set (0.00 sec)
MariaDB [hellodb]> Ctrl-C -- exit!
Aborted