how to find previous & forward relation of data in single query - sql-server

Question

I have table :
ID Person_ID Person_Relative_ID
1 10 20
2 20 30
3 13 15
4 30 40
5 55 56
6 40 50
Here we can see the person & person_relative_id chain is going like 10 - 20 - 30 - 40 - 50
Now if user search Person_Relative_ID of person_id = 20 then result would be like: [All its relation]
Person_Relative_ID
10
30
40
50
Or user want to search Person_Relative_ID for person_id = 40 . then result like
Person_Relative_ID
10
20
30
50
Or user want to search Person_Relative_ID for person_id = 50 . then result like
Person_Relative_ID
10
20
30
40
Any suggestion really appreciated.

Answer 1

Well I'm not sure this is the most performance effective solution, and I'd have liked to deal with a single recursive CTE instead of two, but this works at least.
Just replace the references to the temporary table I used to test this, with your real table. But what it does, is it uses two recursive CTE's to find all references above (CTEUp) and below (CTEDown) your ID, and then shows them in order, except for your searched ID.
Note: This is for SQL Server, not Oracle.
-- Creating dummy variables for testing
DECLARE #PERSONS TABLE (ID INT IDENTITY(1,1), Person_ID INT, Person_Relative_ID INT)
INSERT INTO #PERSONS VALUES (10,20), (20,30), (13,15), (30,40), (55,56), (40,50)
-- Variable for searched ID, the actual script begins here
DECLARE #SEARCHED_ID INT
SET #SEARCHED_ID = 20
;WITH CTEUp AS
-- Fetching all relations above the ID
(SELECT Person_ID
FROM #PERSONS
WHERE Person_ID = #SEARCHED_ID
UNION ALL
SELECT Person_Relative_ID
FROM #PERSONS P
JOIN CTEUp C ON C.Person_ID = P.Person_ID
AND P.Person_Relative_ID > C.Person_ID)
, CTEDown AS
-- Fetching all relations below the ID
(SELECT Person_ID
FROM #PERSONS
WHERE Person_Relative_ID = #SEARCHED_ID
UNION ALL
SELECT P.Person_ID
FROM #PERSONS P
JOIN CTEDown C ON C.Person_ID = P.Person_Relative_ID
AND P.Person_ID < C.Person_ID)
-- Showing results
SELECT Person_ID
FROM
(SELECT *
FROM CTEDown
UNION ALL
SELECT *
FROM CTEUp) SRC
WHERE Person_ID <> #SEARCHED_ID --... minus the ID, as per your example
ORDER BY Person_ID ASC

Answer 2

Just gave a try in Oracle, could be better but still it works
with tab(ID, Person_ID, Person_Relative_ID) as (
SELECT 1, 10, 20 from dual union all
SELECT 2, 20, 30 from dual union all
SELECT 3, 13, 15 from dual union all
SELECT 4, 30, 40 from dual union all
SELECT 5, 55, 56 from dual union all
SELECT 6, 40, 50 from dual),
---------
--End of data preparation
---------
filter_tab as (
select 40 as id from dual), --> Put the search id here
final_tab(person_id) as (
select person_id
from tab
start with person_relative_id = (select id from filter_tab)
connect by prior person_id = person_relative_id
union
select person_relative_id
from tab
start with person_id = (select id from filter_tab)
connect by prior person_relative_id = person_id)
select *
from final_tab
where not exists (select 'x'
from filter_tab
where id = person_id )
order by 1;
Output:
PERSON_ID
---------
10
20
30
50
I just traversed to both ends from the start point, did union of the result and excluded the search id.

Answer 3

In SQL Server 2012 and above, you can use LAG and LEAD function.
Here is a sample:
SELECT TOP 1000 [n], LAG([n]) OVER(ORDER BY [n] ), LEAD([n]) OVER (ORDER BY [n])
FROM [dbo].[Nums]
it generates results:
n LAG LEAD
1 NULL 2
2 1 3
3 2 4
4 3 5
5 4 6

Answer 4

If you are using SQL2005 and above, SQL Recursive CTE structured SQL query can be used for querying hierarchical data models like in your case
Below query uses also multiple CTE queries to prevent usage of unnecessary temp tables or table variables
declare #id smallint = 50
;with cte as (
select Person_ID, Person_Relative_ID
from PersonRelative
where Person_ID = #id OR Person_Relative_ID = #id
union all
select P.Person_ID, P.Person_Relative_ID
from PersonRelative P
inner join CTE on CTE.Person_ID = P.Person_Relative_ID
), cte2 as (
select Person_ID from cte
union
select Person_Relative_ID from cte
), cte3 as (
select Person_ID, Person_Relative_ID
from PersonRelative
where Person_ID = #id OR Person_Relative_ID = #id
union all
select P.Person_ID, P.Person_Relative_ID
from PersonRelative P
inner join CTE3 on CTE3.Person_Relative_ID = P.Person_ID
), cte4 as (
select Person_ID from cte3
union
select Person_Relative_ID from cte3
)
select * from cte4 where Person_ID <> #id
union
select * from cte2 where Person_ID <> #id