第十七周作业

第十七周

1、 导入hellodb.sql生成数据库

(1) 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]> select Name as 姓名,Age as 年龄 from students where Age > 25 and Gender = 'M';
+--------------+--------+
| 姓名         | 年龄   |
+--------------+--------+
| 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)

 

(2) 以ClassID为分组依据，显示每组的平均年龄

MariaDB [hellodb]> select Classid as 班级号,avg(Age) as 平均年龄 from students where Classid is not NULL group by classid;
+-----------+--------------+
| 班级号    | 平均年龄     |
+-----------+--------------+
|         1 |      20.5000 |
|         2 |      36.0000 |
|         3 |      20.2500 |
|         4 |      24.7500 |
|         5 |      46.0000 |
|         6 |      20.7500 |
|         7 |      19.6667 |
+-----------+--------------+
7 rows in set (0.00 sec)

(3) 显示第2题中平均年龄大于30的分组及平均年龄

 

MariaDB [hellodb]> select ClassID as 班级号,avg(Age) as 平均年龄 from students  where Classid is not NULL group by Classid having 平均年龄 > 30;
+-----------+--------------+
| 班级号    | 平均年龄     |
+-----------+--------------+
|         2 |      36.0000 |
|         5 |      46.0000 |
+-----------+--------------+
3 rows in set (0.00 sec)

 

(4) 显示以L开头的名字的同学的信息

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)

 

2、数据库授权magedu用户，允许192.168.1.0/24网段可以连接mysql

GRANT ALL ON  *.*  TO 'magedu'@'192.168.1.%' IDENTIFIED BY '123456' ;