SELECT stc_student.id, group_concat(stc_score.teacher_name) as 评分老师,
student_name, ifnull(cast(avg(score) as DECIMAL(18,0)),'') as 平均成绩,
student_class,student_worklinks,created_at FROM stc_score
RIGHT JOIN stc_student ON ( stc_student.id=stc_score.id)
GROUP BY stc_student.id ORDER BY 平均成绩 DESC;
显示：
+-----------+-------------------------------------------+--------------+--------------+---------------+-----------------------+------------+
| id | 评分老师 | student_name | 平均成绩 | student_class | student_worklinks | created_at |
+-----------+-------------------------------------------+--------------+--------------+---------------+-----------------------+------------+
| 100160728 | 汤佳,周耀鹏,徐力,李力亚,evilhui | 王晖 | 64 | 移动1603 | /100160728/index.html | 1493201986 |
| 100160110 | evilhui | 刘杰 | 5 | 移动1603 | 111 | 1495566211 |
| 100160111 | evilhui | 刘杰 | 5 | 移动1603 | 111 | 1495566211 |
| 100160112 | evilhui | 刘杰 | 5 | 移动1603 | 111 | 1495566211 |
| 100160113 | evilhui | 刘杰 | 5 | 移动1603 | 111 | 1495566211 |
| 100160115 | evilhui | 刘杰 | 5 | 移动1603 | 111 | 1495566211 |
| 100160705 | evilhui | 段家峰 | 5 | 移动1601 | /100160705 | 1495812165 |
| 100160713 | evilhui | 徐昶 | 5 | 移动1603 | 健康路记录i | 1495812877 |
| 343544442 | evilhui | 刘杰 | 5 | 移动1603 | asdas | 1495813142 |
| 425688411 | evilhui | 王晖 | 5 | 移动1603 | esfer | 1495815475 |
| 100160729 | 周耀鹏,evilhui | 晓杰 | 43 | 移动1603 | /100160728/index.html | 1493201986 |
| 100160120 | evilhui | 刘杰 | 33 | 移动1603 | 111 | 1495566211 |
| 100160114 | evilhui | 刘杰 | 2 | 移动1603 | 111 | 1495566211 |
| 100160733 | evilhui | 王晖 | 10 | 移动1603 | 暂无 | 1495611800 |
| 111111111 | evilhui | 吕世惠 | 10 | 移动1601 | 晋中地区昔阳县 | 1495811266 |
| 123567777 | evilhui | asd | 10 | 移动1603 | 123213 | 1495813419 |
| 434655555 | evilhui | 阿斯顿 | 10 | 移动1603 | asa | 1495813337 |
| 776766666 | evilhui | 阿斯顿 | 10 | 移动1603 | 还行 | 1495815915 |
| 987654321 | evilhui | 最后测试 | 10 | 移动1602 | 欧美style | 1495814028 |
| 100001111 | NULL | 王晖 | | 移动1603 | NULL | 1495987456 |
| 100001112 | NULL | 王晖 | | 移动1603 | NULL | 1495988224 |
| 100160116 | NULL | 刘杰 | | 移动1603 | 111 | 1495566211 |
| 100160117 | NULL | 刘杰 | | 移动1603 | 111 | 1495566211 |
| 100160118 | NULL | 刘杰 | | 移动1603 | 111 | 1495566211 |
| 100160119 | NULL | 刘杰 | | 移动1603 | 111 | 1495566211 |
| 100160121 | NULL | 刘杰 | | 移动1603 | 111 | 1495566211 |
| 100160122 | NULL | 刘杰 | | 移动1603 | 111 | 1495566211 |
| 100160123 | NULL | 刘杰 | | 移动1603 | 111 | 1495566211 |
| 100160623 | NULL | 郭峰斌 | | 移动1601 | /100160623/index.html | 1495565545 |
| 100160731 | NULL | 吕倩 | | 移动1603 | /100160728/index.html | 1493201986 |
| 100160922 | NULL | 王超 | | 移动1602 | /100160729/index.html | 1493201986 |
| 100160923 | NULL | 王超 | | 移动1603 | /100160729/index.html | 1493201986 |
| 100200300 | NULL | 段家风 | | 移动1603 | | 1495999675 |
| 123134444 | NULL | 王晖 | | 移动1603 | NULL | 1495566211 |
| 130120110 | NULL | 吕林 | | 移动1603 | NULL | 1495999675 |
+-----------+-------------------------------------------+--------------+--------------+---------------+-----------------------+------------+
平均成绩`列未排序
答案 0 :(得分：0)
检查实际的MySQL服务器my.cnf文件。以下将整个链设置为UTF-8：
[client]
default-character-set=utf8mb4
[mysql]
default-character-set=utf8mb4
[mysqld]
collation-server = utf8mb4_unicode_ci
init-connect='SET NAMES utf8mb4'
character-set-server = utf8mb4