How to remove duplicate entry from SQL Table?

CaseProblem table has duplicate entry for CaseDetailId 

Id  CasedetailId

1    20152

2    20152 

3    20153

WITH CTE AS(
   SELECT CaseDetailId,
       RN = ROW_NUMBER()OVER(PARTITION BY CaseDetailId ORDER BY CaseDetailId)
   FROM dbo.CaseProblem
)

--select * FROM CTE WHERE  RN > 1   

 Delete  * FROM CTE WHERE  RN > 1

Final Result 

Id  CasedetailId
1    20152
3    20153
2    20152 this record should be delete.

Order by Parent Child in Sql server

declare @ParentChild table (ChildID int, ParentID int, Name varchar(50))
insert @ParentChild values
 (1, null, 'First Parent'),
 (2, null, 'Second Parent'), 
 (3, 2, 'Second Child 1'), 
 (4, 1, 'First Child 1'), 
 (5, 2, 'Second Child 2'), 
 (6, 1, 'First Child 2');

    select  *
    from    @ParentChild feat
    order by
            case 
            when ParentID is null 
            then Name
            else    (
                    select  Name

                    from    @ParentChild parent 
                    where   parent.ChildID = feat.ParentID
                    ) 
            end
    ,       case when ParentID is null then 1 end desc
    ,       Name