SQL CASE use for NULL values ​​ordered last


Example

in this way '0' representing the known values ​​are ranked first, '1' representing the NULL values ​​are sorted by the last:

SELECT ID
      ,REGION
      ,CITY
      ,DEPARTMENT
      ,EMPLOYEES_NUMBER
  FROM DEPT
  ORDER BY 
  CASE WHEN REGION IS NULL THEN 1 
  ELSE 0
  END, 
  REGION
IDREGIONCITYDEPARTMENTEMPLOYEES_NUMBER
10Mid-AtlanticPhiladelphiaRESEARCH13
14Mid-AtlanticNew YorkSALES12
9MidwestChicagoSALES8
12New EnglandBostonMARKETING9
5WestLos AngelesRESEARCH11
15NULLSan FranciscoMARKETING12
4NULLChicagoINNOVATION11
2NULLDetroitHUMAN RESOURCES9