Get parents and children given a segment in a recursion SQL - sql-server

Question

Given an ID at the beginning or middle or end, I want to look up for all the rows that are linked between them.
With this I found the child elements recursively
declare #T table(
Id int primary key,
Name nvarchar(255) not null,
ParentId int)
insert into #T values
(1, 'A', NULL),
(2, 'B', 1),
(3, 'C', 2),
(4, 'D', NULL),
(5, 'E', 1)
declare #Id int = 2
;with cte as
(
select T.*
from #T as T
where T.Id = #Id
union all
select T.*
from #T as T
inner join cte as C
on T.ParentId = C.Id
)
select *
from cte
If #Id is equals 2, I will get 2 and 3. But I want to retrieve the parent too, in this case 1.
I want to get this:
If id = 1
1 A NULL
2 B 1
3 C 2
5 E 1
If id = 2
1 A NULL
2 B 1
3 C 2
5 E 1
If id = 3
1 A NULL
2 B 1
3 C 2
5 E 1
If id = 4
4 D NULL
IF id = 5
1 A NULL
2 B 1
3 C 2
5 E 1
How can I fix this?

Answer 1

Ok! I've got you:
I created a separate family for testing.
The first thing you need to do is create a query to find the oldest ancestor of your chosen ID. That is the first CTE below. Then you designate that, I called it #Eve and find Eve, all children of Eve.
Here is the example you can play around with
create table UserType (
Id int,
name nvarchar(255),
parentid int)
insert into UserType values
(1, 'A', NULL),
(2, 'B', 1),
(3, 'C', 2),
(4, 'D', NULL),
(5, 'E', 1),
(6, 'F', NULL),
(7, 'G', 6),
(8, 'H', 7);
DECLARE #eve BIGINT; --ancestor
DECLARE #id BIGINT;
SET #id = 8; --This is where you choose
WITH tblParent AS --CTE for oldest ancestor
(
SELECT *
FROM UserType WHERE Id = #id
UNION ALL
SELECT UserType.*
FROM UserType JOIN tblParent ON UserType.Id = tblParent.ParentId
)
select
#eve = (select top 1 id from tblParent order by id);
WITH tblChild AS --CTE for all #eve and all children
(
SELECT *
FROM UserType WHERE id = #eve
UNION ALL
SELECT UserType.* FROM UserType JOIN tblChild ON UserType.ParentId = tblChild.Id
)
SELECT * FROM tblChild
order by id
OPTION(MAXRECURSION 32767)
Props to CodeProject which was quite helpful.

Answer 2

Try something like this.
declare #tbl table( --test table var
Id int,
name nvarchar(255),
parentid int)
insert into #tbl values -- test data
(1, 'A', NULL),
(2, 'B', 1),
(3, 'C', 2),
(4, 'D', NULL),
(5, 'E', 1),
(6, 'F', NULL),
(7, 'G', 6),
(8, 'H', 7);
declare #id int = 7
;with parents as (
select id,name,parentid, 0 lvl
from #tbl
where id=#id
union all
select t.id,t.name,t.parentid, lvl-1
from #tbl t
inner join parents p on t.Id=p.parentid --up the tree
)
,children as (
select id,name,parentid, 0 lvl
from #tbl
where id=#id --select single record
union all
select t.id,t.name,t.parentid, lvl+1
from #tbl t
inner join children c on c.Id=t.parentid -- down the tree
)
select * from parents
union --combine results
select * from children
order by lvl