如何获取子记录的父母、祖父母等及其本身以及 SQL 中与根的距离

Question

I have a table as shown below -

    ID | NAME        | PARENT

     1 | Global      | null 
     2 | USA         | 1
     3 | Canada      | 1
     4 | USA-1       | 2
     5 | USA-11      | 4

The column parent refers to the column id ie, Global is the root. For USA-11, USA-1 is the parent, USA is the grandparent and Global is the great grand parent. It is a rugged hierarchy and can go upto any level . I need help in writing a query that will expand this hierarchy in the following manner -

    ID | NAME        | PARENT    | Distance_from_parent

     1 | Global      | Global    | 0
     2 | USA         | USA       | 0
     2 | USA         | Global    | 1
     3 | Canada      | Canada    | 0
     3 | Canada      | Global    | 1
     4 | USA-1       | USA-1     | 0
     4 | USA-1       | USA       | 1
     4 | USA-1       | Global    | 2
     5 | USA-11      | USA-11    | 0
     5 | USA-11      | USA-1     | 1
     5 | USA-11      | USA       | 2
     5 | USA-11      | Global    | 3

So if you notice, I'm repeating every location name against itself and its hierarchy. The column "distance_from_parent" is the distance from the parent mentioned in the "Parent" column.

I have tried this using Connect By, Level and prior, but unable to achieve this kind of output.

The DDL for this is -

create table subsidiary (id number, name varchar2(50), parent number); 

insert into subsidiary (id, name, parent) values (1, 'Parent', null);
insert into subsidiary (id, name, parent) values (2, 'USA', 1);
insert into subsidiary (id, name, parent) values (3, 'Canada', 1);
insert into subsidiary (id, name, parent) values (4, 'USA-1', 2);
insert into subsidiary (id, name, parent) values (5, 'USA-11', 4);

Answer 1

Use a hierarchical query with CONNECT_BY_ROOT :

SELECT CONNECT_BY_ROOT( ID ) AS id,
       CONNECT_BY_ROOT( name ) AS name,
       name AS parent,
       LEVEL - 1 AS distance_from_parent
FROM   subsidiary
CONNECT BY PRIOR parent = id
ORDER BY id, distance_from_parent;

So for your test data:

CREATE TABLE subsidiary ( ID, NAME, PARENT ) AS
SELECT 1, 'Global', null FROM DUAL UNION ALL 
SELECT 2, 'USA',    1 FROM DUAL UNION ALL
SELECT 3, 'Canada', 1 FROM DUAL UNION ALL
SELECT 4, 'USA-1',  2 FROM DUAL UNION ALL
SELECT 5, 'USA-11', 4 FROM DUAL;

This outputs:

 ID | NAME | PARENT | DISTANCE_FROM_PARENT -: |:----- |:----- |  -------------------: 1 |  Global | Global | 0 2 |  USA | USA | 0 2 |  USA | Global | 1 3 |  Canada | Canada | 0 3 |  Canada | Global | 1 4 |  USA-1 | USA-1 | 0 4 |  USA-1 | USA | 1 4 |  USA-1 | Global | 2 5 |  USA-11 | USA-11 | 0 5 |  USA-11 | USA-1 | 1 5 |  USA-11 | USA | 2 5 |  USA-11 | Global | 3 

db<>fiddle here

Answer 2

You can use CONNECT BY to get your desired results:

SELECT s.id, s.name, CONNECT_BY_ROOT(s.name) AS ROOT_NAME, LEVEL-1 AS ROOT_DISTANCE
FROM subsidiary s
CONNECT BY s.parent = PRIOR(s.id)
ORDER BY s.id, LEVEL;

Here is a SQLFiddle with this solution. ( Link )