MySql Recursive - get all children and parents from a given id - mysql

Question

MySQL Version 8.0
Schema SQL
CREATE TABLE IF NOT EXISTS `department` (
`id` INT NOT NULL,
`name` VARCHAR(45) NOT NULL,
`father` INT NULL,
PRIMARY KEY (`id`),
INDEX `fk_department_department_idx` (`father` ASC) VISIBLE,
CONSTRAINT `fk_department_department`
FOREIGN KEY (`father`)
REFERENCES `department` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
insert into department (id,name,father)
values
(1, 'dp1',null),
(2, 'dp2',null),
(3, 'dp3',1),
(4, 'dp4',1),
(5, 'dp5',2),
(6, 'dp6',4),
(7, 'dp7',6),
(8, 'dp8',6),
(9, 'dp9',6);
SET GLOBAL sql_mode=(SELECT REPLACE(##sql_mode,'ONLY_FULL_GROUP_BY',''));
SET SESSION sql_mode = '';
My query:
WITH RECURSIVE cte_department AS (
SELECT
d1.id,
d1.name,
d1.father
FROM
department d1
WHERE
d1.id=6
UNION ALL
SELECT
d2.id,
d2.name,
d2.father
FROM
department d2
INNER JOIN cte_department cte ON cte.id = d2.father
)
SELECT * FROM cte_department;
Result:
id name father
6 dp6 4
7 dp7 6
8 dp8 6
9 dp9 6
What I need:
id name father
1 dp1 null
4 dp4 1
6 dp6 4
7 dp7 6
8 dp8 6
9 dp9 6
The problem is:
I can get all childrens, but I need to add to this query all the parents from the given ID, in this case, the ID 6.
I'm stuck with that. If someone can help me, follow the fiddle.
https://www.db-fiddle.com/f/g8YkE3hqsvaw8G9vdHPyyF/0

Answer 1

The recursive part can have multiple query blocks.
WITH RECURSIVE cte_department AS (
SELECT
d1.id,
d1.name,
d1.father,
'Begin' state
FROM
department d1
WHERE
d1.id=6
UNION ALL
SELECT
d2.id,
d2.name,
d2.father,
'Up'
FROM
department d2
INNER JOIN
cte_department cte
ON
cte.father = d2.id
WHERE
cte.state in ('Begin', 'Up')
UNION ALL
SELECT
d2.id,
d2.name,
d2.father,
'Down'
FROM
department d2
INNER JOIN
cte_department cte
ON
cte.id = d2.father
WHERE
cte.state in ('Begin', 'Down')
)
SELECT
id, name, father
FROM
cte_department
ORDER BY
father, id, name;
Try it on db<>fiddle.

Answer 2

I would use two separate recursive queries: one to bring the children, the other for the parents, and then union the results. You can keep track of the level of each node to properly order the records int he resultset:
with recursive
children as (
select 1 as lvl, d.* from department d where id = 6
union all
select c.lvl, d.* from department d inner join children c on c.id = d.father
),
parents as (
select 1 as lvl, d.* from department d where id = 6
union all
select p.lvl - 1, d.* from department d inner join parents p on d.id = p.father
)
select * from parents
union -- on purpose, to remove the duplicate on id 6
select * from children
order by lvl;
This is safer than having multiple union all members in the same query. MySQL does not guarantee the order of evaluation of the members in the recursion, so using this technique could lead to unexpected behavior.
Demo on DB Fiddle
Unrelated to your question, but: the following can be seen in your code:
SET GLOBAL sql_mode=(SELECT REPLACE(##sql_mode,'ONLY_FULL_GROUP_BY',''));
SET SESSION sql_mode = '';
Just don't. ONLY_FULL_GROUP_BY is there for a good reason, that is to have MySQL behave consistenly with the SQL standard as regard to aggregation query. Disabling this SQL mode is never a good idea.