Get child hierarchy for a subset of users - sql

Question

I have a customer table where there can be a hierarchy of parent-child records.
The customer table has a structure like,
customer {
id integer,
user_id integer,
parent_id integer
}
Given an user_id I know how to fetch all child users in hierachy that belong to the given user_id. For example for user_id value of 100,
WITH RECURSIVE subordinates AS (
SELECT c1.*
FROM customer c1
WHERE c1.user_id = 100
UNION
SELECT c2.*
FROM customer c2
INNER JOIN subordinates s
ON s.id = c2.parent_id)
SELECT * FROM subordinates;
But I would like to restrict the output of above query to a subset of users. So the first argument to the above query will be a parent user_id (let's call it parent_user) and the second argument will be a list of user_id (let's call it child_users).
What I would like to do is,
Iterate over child_users
Check if child_user in child_users is a child of parent_user
If yes, fetch entire child hierachy of child_user
Can above 3 steps be achieved in a single sql query. Plese suggest.
EDIT
The sample table data can be,
id user_id parent_id
-----------------------
1 100 null
2 101 100
3 102 101
4 103 102
5 104 100
6 105 null
So given above data in the table, for input values of parent_user = 100 and child_users = [101, 105] I am expetcting to retrieve following output,
id user_id parent_id
-----------------------
2 101 100
3 102 101
4 103 102
The record with id = 5 should't be part of the output even though it has parent_id = 100 since user_id 104 is not in the child_users list.

Answer 1

Please see the answers below and let me know if that works
declare #Customer table ( Id int,userID int,parentID int)
insert #Customer (Id, userID, parentID)
select 1,100,null union all <br/>
select 1,101,100 union all <br/>
select 1,102,101 union all <br/>
select 1,103,102 union all <br/>
select 1,104,100 union all <br/>
select 1,105,null <br/>
;with cte_emp as <br/>
( <br/>
select ID,userID,parentID
from #Customer
where parentID=100 and userID in (101,105) <br/>
union all <br/>
select e.ID,e.userID,e.parentID
from #Customer e join cte_emp cte
on cte.userid=e.parentID <br/>
) <br/>
select * from cte_emp <br/>

Answer 2

If I follow you correctly, you want to filter on the immediate parent of the starting node. You can just put that condition in the anchor of the CTE:
with recursive subordinates as (
select c.*
from customer
where user_id = any($1) and parent_id = $2
union all
select c.*
from customer c
inner join subordinates s on s.id = c.parent_id
)
select * from subordinates;
Note that I changed the query to accept to input parameters:
$1 is an array of child ids
$2 is the id of the parent that is used to filter