如何在一个以逗号分隔的列表中的一个字段中连接MySQL中的多对多关系中的数据？

Question

我和人事部门之间有多对多的关系,因为一个人可以在很多部门工作.

People          Departments
------          -----------
pID  pName      deptID   deptName
1    James      1        Engineering
2    Mary       2        Research
3    Paul       3        Marketing
                4        Communications

People_Departments
------------------
pID   deptID
1     1
1     2
2     2
2     4
3     1
3     2
3     3

我想要的是这个:

pName  deptName
James  Engineering, Research
Mary   Research, Communication
Paul   Engineering, Research, Marketing

如果我使用下面的SQL在表上执行简单的LEFT JOIN,我将获得与一个人相关的几行:

SELECT people.pName,
       departments.deptName
FROM people
LEFT JOIN people_departments ON people.pID=people_departments.pID
LEFT JOIN departments ON people_departments.deptID=departments.deptID

我尝试了各种组合,GROUP_CONCAT但没有运气.

有什么想法可以分享？

Answer 1

    SELECT people.pName,
           GROUP_CONCAT(departments.deptName SEPARATOR ', ') deptName
      FROM people
 LEFT JOIN people_departments 
        ON people.pID = people_departments.pID
INNER JOIN departments 
        ON people_departments.deptID = departments.deptID
  GROUP BY people.pID

输出:

+-------+----------------------------------+
| pName | deptName                         |
+-------+----------------------------------+
| James | Engineering, Research            |
| Mary  | Research, Communications         |
| Paul  | Engineering, Research, Marketing |
+-------+----------------------------------+
3 rows in set (0.00 sec)