Simple hierarchical query display

How to output this in Postgresql and Sql Server?

 emp_id |            emp_name
--------+---------------------------------
      1 | President
      2 |   Vice President
      3 |     CEO
      4 |     CTO
      5 |       Group Project Manager
      6 |         Project Manager 1
      8 |           Team Leader 1
      9 |             Software Engineer 1
     10 |             Software Engineer 2
     11 |           Test Lead 1
     12 |             Tester 1
     13 |             Tester 2
      7 |         Project Manager 2
     14 |           Team Leader 2
     15 |             Software Engineer 3
     16 |             Software Engineer 4
     17 |           Test Lead 2
     18 |             Tester 3
     19 |             Tester 4
     20 |             Tester 5

Let's make a table named emp first:

select *
into emp
from 
(values
(1, 'President', NULL),
(2, 'Vice President', 1),
(3, 'CEO', 2),
(4, 'CTO', 2),
(5, 'Group Project Manager', 4),
(6, 'Project Manager 1', 5),
(7, 'Project Manager 2', 5),
(8, 'Team Leader 1', 6),
(9, 'Software Engineer 1', 8),
(10, 'Software Engineer 2', 8),
(11, 'Test Lead 1', 6),
(12, 'Tester 1', 11),
(13, 'Tester 2', 11),
(14, 'Team Leader 2', 7),
(15, 'Software Engineer 3', 14),
(16, 'Software Engineer 4', 14),
(17, 'Test Lead 2', 7),
(18, 'Tester 3', 17),
(19, 'Tester 4', 17),
(20, 'Tester 5', 17)
) as x(emp_id, emp_name, mgr_id)

Postgresql version:

with recursive org(emp_id, emp_name, emp_level, mgr_id, sort) as
(
 select  
  a.emp_id, a.emp_name, 0, a.mgr_id,  
  a.emp_name
 from emp a
 where a.mgr_id is null

 union all

 select 
  b.emp_id, b.emp_name, emp_level + 1, b.mgr_id, 
  -- i think this is quickbooks style sorting, saw it first there
  sort || ' : ' || b.emp_name
 from emp b
 join org on org.emp_id = b.mgr_id
)
select 
 emp_id, repeat(' ', emp_level * 2) || emp_name as emp_name
  
 /* uncomment the following if you want to see the full path of 
 employee up to its president */
 -- ,sort 
from org
order by sort

Sql Server version:

with org(emp_id, emp_name, emp_level, mgr_id, sort) as
(
 select  
  a.emp_id, a.emp_name, 0, a.mgr_id,  
  convert(varchar(8000), a.emp_name)  
 from emp a
 where a.mgr_id is null

 union all

 select 
  b.emp_id, b.emp_name, emp_level + 1, b.mgr_id, 
  -- i think this is quickbooks style sorting, saw it first there
  sort + ' : ' + b.emp_name
 from emp b
 join org on org.emp_id = b.mgr_id
)
select 
 emp_id, 
 emp_name = REPLICATE(' ',emp_level * 2) + emp_name
 /* uncomment the following if you want to see the full path of 
 employee up to its president */
 -- sort 
from org
order by sort

Uncomment the sort to infer how it facilitated the hierarchical display of records