mysql join不返回所需的结果

Question

My data looks like the following,

employeeId  ManagerId
 3            2
 4            2
 2            1
 5            1
 6            3

An employee has a manager and that manager will/could have a manager. What i would like to do is get the manager of an employee and the manager of that manager should it be available.

For eg For employee 6 the result will be 3 & 2. For employee 2 it will be 1.

The key requirement here is that the query should return minimum one manager if available and max two levels and no higher. The example given for employee 6 illustrates that.

Right now my query looks like,

 select a.managerId firstManager,b.ManagerId secondManager
 from (
 select managerId from Results where employeeId = 6  ) a 
  join 
 (select managerId from Results where employeeId in (select managerId from  Results where employeeId = 6 ) )b ;

My query works for employee 6 but not for employee 2. dbfiddle

Answer 1

You can try the below - with recursive cte: DEMO

with RECURSIVE t as
(
select employeeid,managerid from Results where employeeid=6 
union all
SELECT e.employeeid,e.managerid from Results e inner join t t1 on e.employeeid = t1.managerid
) 
select * from t order by managerid desc limit 2

Answer 2

You can do a self join and you will get the results you require. dbfiddle

Select a.employeeId,
       a.ManagerId First_Manager, 
       b.ManagerId Second_Manager 
from Results a
left join Results b
on a.ManagerId = b.employeeId

Output:

EmployeeId  First_Manager   Second_Manager
3   2   1
4   2   1
2   1   null
5   1   nul
6   3   2