第十一周作业

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

# students表

mysql> 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)

# 查询结果

mysql[hellodb]> select name,age from students  where Age>25 and Gender='M';

+--------------+-----+
| name         | age |
+--------------+-----+
| Xie Yanke    |  53 |
| Ding Dian    |  32 |
| Yu Yutong    |  26 |
| Shi Qing     |  46 |
| Tian Boguang |  33 |
| Xu Xian      |  27 |
| Sun Dasheng  | 100 |
+--------------+-----+

 

(2) 以ClassID为分组依据，显示每组的平均年龄

mysql[hellodb]> select classid 班级,avg(age) 平均年龄 from students group by classid;

+--------+--------------+
| 班级   | 平均年龄     |
+--------+--------------+
|      2 |      36.0000 |
|      1 |      20.5000 |
|      4 |      24.7500 |
|      3 |      20.2500 |
|      5 |      46.0000 |
|      7 |      19.6667 |
|      6 |      20.7500 |
|   NULL |      63.5000 |
+--------+--------------+
8 rows in set (0.00 sec)

mysql[hellodb]> select classid 班级,avg(age) 平均年龄 from students where classid is not null group by classid;

+--------+--------------+
| 班级   | 平均年龄     |
+--------+--------------+
|      2 |      36.0000 |
|      1 |      20.5000 |
|      4 |      24.7500 |
|      3 |      20.2500 |
|      5 |      46.0000 |
|      7 |      19.6667 |
|      6 |      20.7500 |
+--------+--------------+
7 rows in set (0.00 sec)

mysql[hellodb]> select classid 班级,avg(age) 平均年龄 from students group by classid having classid is not null;

+--------+--------------+
| 班级   | 平均年龄     |
+--------+--------------+
|      2 |      36.0000 |
|      1 |      20.5000 |
|      4 |      24.7500 |
|      3 |      20.2500 |
|      5 |      46.0000 |
|      7 |      19.6667 |
|      6 |      20.7500 |
+--------+--------------+
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

mysql[hellodb]> select classid 班级,avg(age) 平均年龄 from students where classid is not null group by classid having 平均年龄 > 30;

+--------+--------------+
| 班级   | 平均年龄     |
+--------+--------------+
|      2 |      36.0000 |
|      5 |      46.0000 |
+--------+--------------+
2 rows in set (0.00 sec)

mysql[hellodb]> select classid 班级,avg(age) 平均年龄 from students group by classid having classid is not null and 平均年龄 > 30;

+--------+--------------+
| 班级   | 平均年龄     |
+--------+--------------+
|      2 |      36.0000 |
|      5 |      46.0000 |
+--------+--------------+
2 rows in set (0.00 sec)

 

(4) 显示以L开头的名字的同学的信息

mysql[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

mysql> create user magedu@'192.168.1.%' identified by 'time9818';

#查看指定用户获得的授权
mysql> show grants for  'magedu'@'192.168.1.%';
+----------------------------------------------+
| Grants for magedu@192.168.1.%                |
+----------------------------------------------+
| GRANT USAGE ON *.* TO `magedu`@`192.168.1.%` |
+----------------------------------------------+
1 row in set (0.00 sec)

#刷新权限
mysql> flush privileges;