GROUP_CANCAT([distinct] str [order by str asc/desc] [separator])
将group by产生的同一个分组中的值连接起来,返回一个字符串结果。
示例:查询每个部门的员工姓名
示例:
mysql> select deptno,group_concat(ename)
-> from emp
-> group by deptno;
+--------+--------------------------------------+
| deptno | group_concat(ename) |
+--------+--------------------------------------+
| 10 | clark,king,miller |
| 20 | smith,jones,scott,adams,ford |
| 30 | allen,ward,martin,blake,turner,james |
+--------+--------------------------------------+