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

'07:39:59(root@localhost) [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 (0.11 sec)

(2) 以ClassID为分组依据，显示每组的平均年龄

'07:42:40(root@localhost) [hellodb]'> select classid,avg(age) from students group by classid;
+---------+----------+
| classid | avg(age) |
+---------+----------+
|       2 |  36.0000 |
|       1 |  20.5000 |
|       4 |  24.7500 |
|       3 |  20.2500 |
|       5 |  46.0000 |
|       7 |  19.6667 |
|       6 |  20.7500 |
|    NULL |  49.7500 |
+---------+----------+
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

'07:55:32(root@localhost) [hellodb]'> select cid,avg from (select classid as cid,avg(age) as avg from students group by classid) as avgtb  where avg > 30;
+------+---------+
| cid  | avg     |
+------+---------+
|    2 | 36.0000 |
|    5 | 46.0000 |
| NULL | 49.7500 |
+------+---------+
3 rows in set (0.00 sec)

(4) 显示以L开头的名字的同学的信息

'08:00:19(root@localhost) [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

'08:01:07(root@localhost) [hellodb]'> create user 'magedu'@'192.168.1.%' identified by '123456';
Query OK, 0 rows affected (0.13 sec)

'08:06:19(root@localhost) [hellodb]'> grant select on hellodb.* to magedu@'192.168.156.%';
Query OK, 0 rows affected (0.00 sec)

'08:07:33(root@localhost) [hellodb]'> show processlist;
+----+-----------------+-----------------------+---------+---------+------+------------------------+------------------+
| Id | User            | Host                  | db      | Command | Time | State                  | Info             |
+----+-----------------+-----------------------+---------+---------+------+------------------------+------------------+
|  5 | event_scheduler | localhost             | NULL    | Daemon  | 1747 | Waiting on empty queue | NULL             |
|  8 | root            | localhost             | hellodb | Query   |    0 | init                   | show processlist |
| 11 | magedu          | 192.168.156.204:54828 | NULL    | Sleep   |   41 |                        | NULL             |
+----+-----------------+-----------------------+---------+---------+------+------------------------+------------------+
3 rows in set (0.00 sec)

'08:08:50(root@localhost) [hellodb]'>