需求：

  2. People          Departments
  3. ------          -----------
  4. pID  pName      deptID   deptName
  5. 1    James      1        Engineering
  6. 2    Mary       2        Research
  7. 3    Paul       3        Marketing
  8.                 4        Communications
  10. People_Departments
  11. ------------------
  12. pID   deptID
  13. 1     1
  14. 1     2
  15. 2     2
  16. 2     4
  17. 3     1
  18. 3     2
  19. 3     3
  21. 需求 结果
  23. pName  deptName
  24. James  Engineering, Research
  25. Mary   Research, Communication
  26. Paul   Engineering, Research, Marketing

解决方式：


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


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