从 sql 数据库中的结构化表创建树结构

Question

I have a table that tracks movement of data, it looks like:

From_Id	To_Id
NULL	1
1	2
NULL	3
3	4
4	5
4	6
5	7
6	10
2	8
8	9
5	9
9	NULL
10	NULL

I want to structure and store every possible paths (eg 1,2,8,9) and im unsure about the best possible way to do this with SQL.

I started off with a simple while loop, but got a problem at id=4 where it gets 2 new paths. I tried finding a solution which uses a tree structure, but I couldnt find anything that fits my case.

What is a good solution here?

Edit: Im using microsoft sql server desired output:

From_Id	To_Id	path
NULL	1	1,
1	2	1,2,
NULL	3	3,
3	4	3,4,
4	5	3,4,5,
4	6	3,4,6,
5	7	3,4,5,7,
6	10	3,4,6,10,
2	8	1,2,8,
8	9	1,2,8,9,
5	9	3,4,5,9,
9	NULL	NULL
10	NULL	NULL

I tried this from How to call a recursive function in sql server

DECLARE @TABLE2 TABLE(
    From_Id INT,
    To_id INT
)

INSERT INTO @TABLE2 SELECT NULL,1
INSERT INTO @TABLE2 SELECT 1,2
INSERT INTO @TABLE2 SELECT NULL,3
INSERT INTO @TABLE2 SELECT 3,4
INSERT INTO @TABLE2 SELECT 4,5
INSERT INTO @TABLE2 SELECT 4,6
INSERT INTO @TABLE2 SELECT 5,7
INSERT INTO @TABLE2 SELECT 6,10
INSERT INTO @TABLE2 SELECT 2,8
INSERT INTO @TABLE2 SELECT 8,9
INSERT INTO @TABLE2 SELECT 5,9
INSERT INTO @TABLE2 SELECT 9,NULL
INSERT INTO @TABLE2 SELECT 10,NULL

;WITH Recursives AS (
        SELECT  *,
                CAST(To_id AS VARCHAR(MAX)) + ',' ID_Path
        FROM    @TABLE2
        WHERE   From_Id IS NULL
        UNION ALL
        SELECT  t.*,
        r.ID_Path + CAST(t.To_id AS VARCHAR(MAX)) + ','
        FROM    @TABLE2 t INNER JOIN
                Recursives r ON t.From_Id = r.To_id
)

SELECT  *
FROM Recursives

Which gave me an extra row (it gets much larger when i have 10k + rows)

From_Id	To_Id	ID_Path
NULL	1	1,
1	2	1,2,
NULL	3	3,
3	4	3,4,
4	5	3,4,5,
4	6	3,4,6,
5	7	3,4,5,7,
6	10	3,4,6,10
2	8	1,2,8,
8	9	1,2,8,9,
5	9	3,4,5,9,
9	NULL	NULL
9	NULL	NULL
10	NULL	NULL

Answer 1

Create a many-to-many relationship. A new table will be created that will only store id pairs if they exist. In the case of id 4, 2 separate records will be created. Of course, if you want to display records from a new array, you can also use the select command.

The problem arises if the From_Id and To_Id fields come from the same table. In this case, an intermediate table should be created. I will use a simple one here.

An example of a social networking site. We have a user tracking feature. In this way, we create 2 instances of the follower of the user and observe. We cannot create a direct mana-to-many relationship because this cannot directly refer to the same table. We create 2 additional tables. One will save users as followers and the other as followed. It is between these tables that we create a many-to-many relationship.