2022-03-20

1、导入hellodb.sql生成数据库

mysql> source hellodb_innodb.sql
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| hellodb            |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.01 sec)

(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

mysql> use hellodb;
Database changed
mysql> 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 |
+--------------+-----+
7 rows in set (0.00 sec)

(2) 以ClassID为分组依据，显示每组的平均年龄

mysql> select classid,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 (0.00 sec)

(3) 显示第2题中平均年龄大于30的分组及平均年龄

mysql> select classid,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)

(4) 显示以L开头的名字的同学的信息

mysql> 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'@'192.168.1.0/24';
Query OK, 0 rows affected (0.00 sec)

mysql> select user,host from user;
+---------------+----------------+
| user          | host           |
+---------------+----------------+
| magedu        | 192.168.1.0/24 |
| mysql.session | localhost      |
| mysql.sys     | localhost      |
| root          | localhost      |
+---------------+----------------+
4 rows in set (0.00 sec)

2022-03-20

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