Retrieve top-level parent MySQL

Question

I have the following table:

  id  |  parent_id  |  searchable  |  value
--------------------------------------------
  1   |      0      |      0       |    a
           


        

Answer 1

Recursive queries can be done in Newer Mysql, possibly not around back when this was asked.

Get parents and children data where top level parent has a name of "A" or "B" or "C".

RECURSIVE MySQL 8.0 compatibility. https://dev.mysql.com/doc/refman/8.0/en/with.html

The first part gets the parent top level and filters it, the second gets the children joining to their parents.

WITH RECURSIVE tree AS ( 
   SELECT id, 
          name, 
          parent_id,
          1 as level 
   FROM category
   WHERE parent_id = 0 AND (name = 'A' or name = 'B' or name = 'C')

   UNION ALL 

   SELECT c.id,
          c.name,
          c.parent_id, 
          t.level + 1
   FROM category c
     JOIN tree t ON c.parent_id = t.id
)
SELECT *
FROM tree;

To find if the parent or one of its children have searchable, you can pull through that value with a COALESCE(NULLIF(p.searchable,0), NULLIF(c.searchable,0)) and by pulling through the top level parent id and joining back against it.

So to initialize your example data:

CREATE TABLE `category`  (
  `id` int(11) NOT NULL,
  `parent_id` int(11) NULL DEFAULT NULL,
  `searchable` int(11) NULL DEFAULT NULL,
  `value` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;

INSERT INTO category (id, parent_id, searchable, value) VALUES
(1,0,0,'a'),
(2,1,0,'b'),
(3,2,1,'c'),
(4,0,0,'d'),
(5,4,1,'e'),
(6,0,0,'f'),
(7,6,0,'g'),
(8,6,0,'h'),
(9,0,1,'i');

And to answer the question.

WITH RECURSIVE tree AS ( 
   SELECT id, 
                  value,
          parent_id,
          1 as level,
                  searchable,
                    id AS top_level_id
   FROM category
   WHERE parent_id = 0

   UNION ALL 

   SELECT c.id,
          c.value,
          c.parent_id, 
          t.level + 1,
                  COALESCE(NULLIF(t.searchable,0), NULLIF(c.searchable,0)),
                    COALESCE(t.top_level_id) AS top_level_id
   FROM category c
     JOIN tree t ON c.parent_id = t.id
)
SELECT category.*
FROM category
LEFT JOIN tree ON tree.top_level_id = category.id
WHERE tree.searchable = 1;

Note: Does not handle cyclic linkages. If you have those, you need to remove them or constraint it so it does not happen, or add a visited column in much the same way you can bring through the top level id possibly.