MySQL 查询查找所有子元素

Question

我有两个表：

元素 :

id_element	name
elem1	CPV
elem2	CBO
elem3	CPV

育儿（引用元素）

id_element	id_element_elements
elem1	null
elem2	elem1
elem3	elem1
elem4	elem2

在这种情况下，是否有从单个元素中查找所有子元素的查询？

寻找类似的东西：

id_element	id_child
elem1	elem2
elem1	elem3
elem2	elem4

Answer 1

WITH RECURSIVE
cte AS ( SELECT *
         FROM parenting 
         WHERE id_element_elements = 'elem1'
       UNION ALL
         SELECT parenting.*
         FROM cte
         JOIN parenting ON cte.id_element = parenting.id_element_elements )
SELECT id_element_elements id_element, id_element id_child
FROM cte

fiddle

Answer 2

SELECT
p.id_element_elements,p.id_element
FROM elements e 
right join parenting p 
On e.id_element =p.id_element_elements
Where p.id_element_elements is not null