TSQL recursive CTE order - tsql

Question

I am having trouble figuring out how I can use recursive CTEs to order my results recursively. Here is what I mean (this is a simplified dataset):
I have this as input:
declare #sections table (id int, parent int);
insert into #sections values (1, 1);
insert into #sections values (2, 2);
insert into #sections values (3, 2);
insert into #sections values (4, 2);
insert into #sections values (5, 4);
insert into #sections values (6, 1);
insert into #sections values (7, 6);
insert into #sections values (8, 6);
insert into #sections values (9, 6);
insert into #sections values (10, 9);
-- hierarchical view
--1
-- 6
-- 7
-- 8
-- 10
-- 9
--2
-- 3
-- 4
-- 5
And I want this as output
EDIT: The order of the rows is the important part here
-- id parent depth
-- 1 1 0
-- 6 1 1
-- 7 6 2
-- 8 6 2
-- 10 8 3
-- 9 6 2
-- 2 2 0
This is the best I can do:
with section_cte as
(
select id, parent, 0 'depth' from #sections where id = parent
union all
select cte.id, cte.parent, depth + 1
from #sections s join section_cte cte on s.parent = cte.id where s.id <> s.parent
)
select *from section_cte
Can anyone please help me tweak this query to get what I need?
Thanks!

Answer 1

You missed the part where you need to identify the depth is from the cte
WITH CTE AS (
SELECT
id
, parent
, 0 AS depth
FROM
#sections
WHERE
id=parent
UNION ALL
SELECT
s.id
, s.parent
, c.depth + 1
FROM
#sections s
JOIN CTE c ON s.parent=c.id AND s.id <> s.parent
)
SELECT *
FROM CTE;

Answer 2

During the recursive build, it is a small matter to add a sequence. In the example below, the order is driven by the alphabetical order of the title, but you can use any other available key/sequence.
Declare #Table table (ID int,Pt int,Title varchar(50))
Insert into #Table values (0,null,'Tags'),(1,0,'Transportation'),(2,1,'Boats'),(3,1,'Cars'),(4,1,'Planes'),(5,1,'Trains'),(6,0,'Technology'),(7,6,'FTP'),(8,6,'HTTP'),(9,0,'Finance'),(10,9,'FTP'),(11,9,'401K'),(12,2,'Sail'),(13,2,'Powered'),(14,6,'Internet'),(15,6,'Database'),(16,15,'SQL Server'),(17,15,'MySQL'),(18,15,'MS Access')
Declare #Top int = null --<< Sets top of Hier Try 9
Declare #Nest varchar(25) =' ' --<< Optional: Added for readability
;with cteHB (Seq,ID,Pt,Lvl,Title) as (
Select Seq = cast(1000+Row_Number() over (Order by Title) as varchar(500))
,ID
,Pt
,Lvl=1
,Title
From #Table
Where IsNull(#Top,-1) = case when #Top is null then isnull(Pt,-1) else ID end
Union All
Select Seq = cast(concat(cteHB.Seq,'.',1000+Row_Number() over (Order by cteCD.Title)) as varchar(500))
,cteCD.ID
,cteCD.Pt,cteHB.Lvl+1
,cteCD.Title
From #Table cteCD
Join cteHB on cteCD.Pt = cteHB.ID)
,cteR1 as (Select Seq,ID,R1=Row_Number() over (Order By Seq) From cteHB)
,cteR2 as (Select A.Seq,A.ID,R2=Max(B.R1) From cteR1 A Join cteR1 B on (B.Seq like A.Seq+'%') Group By A.Seq,A.ID )
Select Hier='HierName'
,B.R1
,C.R2
,A.ID
,A.Pt
,A.Lvl
,Title = Replicate(#Nest,A.Lvl) + A.Title
--,A.Seq --<< Normally Excluded, but you can see how the sequence is built
From cteHB A
Join cteR1 B on A.ID=B.ID
Join cteR2 C on A.ID=C.ID
Order By A.Seq --<< Use R1 if Range Keys are used
Returns
Hier R1 R2 ID Pt Lvl Title
HierName 1 19 0 NULL 1 Tags
HierName 2 4 9 0 2 Finance
HierName 3 3 11 9 3 401K
HierName 4 4 10 9 3 FTP
HierName 5 12 6 0 2 Technology
HierName 6 9 15 6 3 Database
HierName 7 7 18 15 4 MS Access
HierName 8 8 17 15 4 MySQL
HierName 9 9 16 15 4 SQL Server
HierName 10 10 7 6 3 FTP
HierName 11 11 8 6 3 HTTP
HierName 12 12 14 6 3 Internet
HierName 13 19 1 0 2 Transportation
HierName 14 16 2 1 3 Boats
HierName 15 15 13 2 4 Powered
HierName 16 16 12 2 4 Sail
HierName 17 17 3 1 3 Cars
HierName 18 18 4 1 3 Planes
HierName 19 19 5 1 3 Trains
Now, you may have noticed R1 and R2. These are my range keys, and are often used to aggregate data without recursion. If you don't need or want these, just remove the cteR1 and cteR2 (and the corresponding references in the final SELECT).
EDIT
You also have the option of selecting a portion of the hierarchy (i.e. Technology and its children).

Answer 3

The trick you need is to create a sortstring which match your business rule. Something like this.
WITH CTE AS (
SELECT
id, parent, 0 AS depth
--For MS SQL Server 2012+
,cast(format(id,'0000') as varchar(max)) sort
--For previous versions
,cast(stuff('0000',5-len(cast(id as varchar)),len(cast(id as varchar)),id) as varchar(max)) sort1
FROM #sections
WHERE id=parent
UNION ALL
SELECT s.id, s.parent, c.depth + 1
,sort + cast(format(s.id,'0000') as varchar(max)) sort
,sort + cast(stuff('0000',5-len(cast(s.id as varchar)),len(cast(s.id as varchar)),s.id) as varchar(max)) sort1
FROM #sections s
inner join CTE c ON s.parent=c.id AND s.id <> s.parent
)
SELECT *
FROM CTE
order by sort --or by sort1 depending on version