mysql使用【附源码】_小卓卓的世界

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

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)  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 WHERE classid IS NOT NULL 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 | +---------+----------+ 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> select classid,AVG(age) as avgage from students where classid is not null group by classid having avgage > 30; +---------+---------+ | classid | avgage  | +---------+---------+ |       2 | 36.0000 | |       5 | 46.0000 | +---------+---------+ 2 rows in set (0.01 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.%' identified by '123456'; Query OK, 0 rows affected (0.00 sec) mysql> grant all privileges on `hellodb`.* to 'magedu'@'192.168.1.%' identified by '123456'; Query OK, 0 rows affected (0.00 sec) mysql> flush privileges; Query OK, 0 rows affected (0.00 sec)

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