导入hellodb.sql生成数据库


MariaDB [hellodb]> source /root/hellodb_innodb.sql

(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,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 (0.001 sec)

(2) 以ClassID为分组依据，显示每组的平均年龄


MariaDB [hellodb]> 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 (0.001 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,avg(age) as 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 (0.000 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 (0.000 sec)