语法：
group_concat([DISTINCT] 要连接的字段 [ORDER BY 排序字段 ASC/DESC] [Separator ‘分隔符‘])
select teachId,studentName from bs_student
| teachId | studentName |
| 1 | 张三 |
| 1 | 李四 |
| 1 | 张三 |
| 2 | 王五 |
按teachId分组，将studentName显示在一行（默认以逗号分割）
select teachId,group_concat(studentName) as name from bs_student group by teachId
teachId |
name |
| 1 | 张三,李四,张三 |
| 2 | 王五 |
按teachId分组，将studentName显示在一行，并对studentName去重（默认以逗号分割）
select teachId,group_concat(DISTINCT studentName) name from bs_student group by teachId
teachId |
name |
| 1 | 张三,李四 |
| 2 | 王五 |
按teachId分组，将studentName显示在一行，并对studentName去重且倒叙排序（默认以逗号分割）
select teachId,group_concat(DISTINCT studentName ORDER BY studentName DESC) name from bs_student group by teachId
teachId |
name |
| 1 | 李四,张三 |
| 2 | 王五 |
按teachId分组，将studentName显示在一行，并对studentName去重且倒叙排序，并以分号分割
select teachId,group_concat(DISTINCT studentName ORDER BY studentName DESC SEPARATOR ‘;‘) name from bs_student group by teachId
teachId |
name |
| 1 | 李四;张三 |
| 2 | 王五 |
原文：https://www.cnblogs.com/yzhmj/p/14889666.html