Question

How I can sort a hierarchical table with CTE query ?

sample table :

|ID|Name  |ParentID|
| 0|      |-1      |
| 1|1     |0       |
| 2|2     |0       |
| 3|1-1   |1       |
| 4|1-2   |1       |
| 5|2-1   |2       |
| 6|2-2   |2       |
| 7|2-1-1 |5       |

and my favorite result is :

|ID|Name  |ParentID|Level
| 0|      |-1      |0
| 1|1     |0       |1
| 3|1-1   |1       |2
| 4|1-2   |1       |2
| 2|2     |0       |1
| 5|2-1   |2       |2
| 7|2-1-1 |5       |3
| 6|2-2   |2       |2

another Sample :

an other sample :

|ID|Name      |ParentID|
| 0|          |-1      |
| 1|Book      |0       |
| 2|App       |0       |
| 3|C#        |1       |
| 4|VB.NET    |1       |
| 5|Office    |2       |
| 6|PhotoShop |2       |
| 7|Word      |5       |

and my favorite result is :

|ID|Name      |ParentID|Level
| 0|          |-1      |0
| 1|Book      |0       |1
| 3|C#        |1       |2
| 4|VB.NET    |1       |2
| 2|App       |0       |1
| 5|Office    |2       |2
| 7|Word      |5       |3
| 6|PhotoShop |2       |2

Answer 1

The hierarchyid datatype is able to represent hierarchical data, and already has the desired sorting order. If you can’t replace your ParentID column, then you can convert to it on the fly:

(Most of this script is data setup, the actual answer is quite small)

declare @t table (ID int not null,Name varchar(10) not null,ParentID int not null)
insert into @t(ID,Name,ParentID)
select 0,''          ,-1 union all
select 1,'Book'      ,0  union all
select 2,'App'       ,0  union all
select 3,'C#'        ,1  union all
select 4,'VB.NET'    ,1  union all
select 5,'Office'    ,2  union all
select 6,'PhotoShop' ,2  union all
select 7,'Word'      ,5

;With Sensible as (
    select ID,Name,NULLIF(ParentID,-1) as ParentID
    from @t
), Paths as (
    select ID,CONVERT(hierarchyid,'/' + CONVERT(varchar(10),ID) + '/') as Pth
    from Sensible where ParentID is null
    union all
    select s.ID,CONVERT(hierarchyid,p.Pth.ToString() + CONVERT(varchar(10),s.ID) + '/')
    from Sensible s inner join Paths p on s.ParentID = p.ID
)
select
    *
from
    Sensible s
        inner join
    Paths p
        on
            s.ID = p.ID
order by p.Pth