SQL Server 2008 - Get the bottom most linked record - sql

Question

I have the following data in my SQL Server database:
Id | Name | LinkedId
---+------+----------
1 | A | 1
2 | B | 2
3 | C | 1
4 | D | 3
5 | E | 4
Now I want to write a stored procedure in which the following record should be shown:
Note: LinkedId has the Id that is associated with that name.
For example: "C" is associated with "A"
Id | Name | LinkedId
---+------+---------
1 | A | 1
2 | B | 2
3 | C | 1
4 | D | 1 //here instead of showing 3, it showed 1 which is the bottom most value in the tree
5 | E | 1 //same case as the above
PROBLEM:
For this scenario according to my limited knowledge I can only think of using JOINS (LEFT, INNER) but that won't be enough in this case to get the bottom most linked id of it.
EDIT (OUTPUT):
I want all the items associated (directly and indirectly) with item "C"
Id | Name |
---+------+
3 | C |
4 | D |
5 | E |

Answer 1

You could use a recursive function
A simple explain, recursive function using CTE is a common table expression that uses itself on caculating. It includes:
Invocation of the routine.
The first invocation of the recursive CTE
consists of one or more CTE_query_definitions joined by UNION ALL,
UNION, EXCEPT, or INTERSECT operators.
Because these query definitions
form the base result set of the CTE structure, they are referred to as
anchor members.
CTE_query_definitions are considered anchor members
unless they reference the CTE itself.
All anchor-member query
definitions must be positioned before the first recursive member
definition, and a UNION ALL operator must be used to join the last
anchor member with the first recursive member.
Recursive invocation of the routine.
The recursive invocation includes one or more
CTE_query_definitions joined by UNION ALL operators that reference the
CTE itself. These query definitions are referred to as recursive
members.
Termination check.
The termination check is implicit;
recursion stops when no rows are returned from the previous
invocation.
Reference link: Recursive query using CTE
Simple Example of Recursive CTE
Cte sql server
DECLARE #SampleData AS TABLE (Id int, Name varchar(10), LinkedId int)
INSERT INTO #SampleData
VALUES (1, 'A', 1), (2, 'B', 2),
(3, 'C', 1),(4, 'D', 3),(5, 'A', 4)
;WITH temp AS
(
SELECT sd.Id, sd.Name, sd.Id AS RootId
FROM #SampleData sd WHERE sd.LinkedId = sd.Id -- Invocation of the routine, in this case it's root node of tree.
UNION ALL
-- Recursive invocation of the routine
SELECT sd.Id, sd.Name, t.RootId AS RootId
FROM temp t
INNER JOIN #SampleData sd ON sd.LinkedId = t.Id AND sd.LinkedId <> sd.Id
-- Termination check: sd.LinkedId = t.Id AND sd.LinkedId <> sd.Id.
-- It make recursive query is not an infinitive loop
)
SELECT t.Id, t.Name, t.RootId AS LinkedId
FROM temp t
OPTION (MAXRECURSION 0) -- this option remove recursive max depth, default is 100.
Demo link: Rextester
For new output, you could change The first invocation of the
recursive CTE
;WITH temp AS
(
SELECT sd.Id, sd.Name, sd.Id AS RootId
FROM #SampleData sd WHERE sd.Id = 3
UNION ALL
-- Recursive invocation of the routine
SELECT sd.Id, sd.Name, t.RootId AS RootId
FROM temp t
INNER JOIN #SampleData sd ON sd.LinkedId = t.Id AND sd.LinkedId <> sd.Id
-- Termination check: sd.LinkedId = t.Id AND sd.LinkedId <> sd.Id.
-- It make recursive query is not an infinitive loop
)
SELECT t.Id, t.Name, t.RootId AS LinkedId
FROM temp t
OPTION (MAXRECURSION 0) -- this option remove recursive max depth, default is 100.

Answer 2

You want a recursive procedure:
with cte as (
select t.id, t.name, t.linkedid, 1 as lev
from t
where t.linkedid = t.id
union all
select t.id, t.name, cte.linkedid, cte.lev + 1
from t join
cte
on cte.id = t.linkedid and t.linkedid <> t.id
)
select id, name, linkedid
from cte;
Here is it working in practice.