MySQL recursive search

Question

I have 5 tables:

library_item
============
id
title
description
index_text

library_item_rel_category
=========================
item_id
category_id

library_category
================
id
parent_id
name

library_item_rel_tag
====================
item_id
tag_id

library_tag
===========
id
name

And currently I have this MySQL request (Using PHP PDO):

SELECT
    i.*,
    ((
        ((MATCH (i.title) AGAINST (:terms)) * 5) +
        ((MATCH (i.description) AGAINST (:terms)) * 4) +
        ((MATCH (i.index_text) AGAINST (:terms)) * 3) +
        (MATCH (i.title, i.description, i.index_text) AGAINST (:terms))
    ) + IFNULL(c.score, 0) + IFNULL(t.score, 0)) as score
FROM 
    library_item AS i
LEFT JOIN
    (
        SELECT
            rel_c.item_id,
            ((MATCH(c.name) AGAINST (:terms)) * 5) AS score
        FROM 
            library_item_rel_category rel_c
        INNER JOIN
            library_category c ON rel_c.category_id = c.id
        WHERE
            MATCH(c.name) AGAINST (:terms)
        ORDER BY
            score DESC
    ) AS c ON c.item_id = i.id
LEFT JOIN
    (
        SELECT
            rel_t.item_id,
            ((MATCH(t.name) AGAINST (:terms)) * 5) AS score
        FROM 
            library_item_rel_tag rel_t
        INNER JOIN
            library_tag t ON rel_t.tag_id = t.id
        WHERE
            MATCH(t.name) AGAINST (:terms)
        ORDER BY
            score DESC
        LIMIT 1
    ) AS t ON t.item_id = i.id
WHERE
    i.is_archive = 0 AND
    ((
        ((MATCH (i.title) AGAINST (:terms)) * 5) +
        ((MATCH (i.description) AGAINST (:terms)) * 4) +
        ((MATCH (i.index_text) AGAINST (:terms)) * 3) +
        (MATCH (i.title, i.description, i.index_text) AGAINST (:terms))
    ) + IFNULL(c.score, 0) + IFNULL(t.score, 0)) > 5
GROUP BY 
    i.id
ORDER BY
    score DESC

I would like to add the ability to match the parent categories too until it hits the root. Is it possible using MySQL in this single query?

I am ready to change table structure if needed, it's my first recursive tree.

Community · Accepted Answer · 2017-05-23 12:27:29Z

1

MySQL does not support recursive queries as some other databases do. There is no way to find all parent categories in a single query with the way you're storing the parent_id.

See my presentation Models for Hierarchical Data with SQL and PHP for an overview of different techniques for storing and querying tree-like structures in MySQL.

See also my answer to What is the most efficient/elegant way to parse a flat table into a tree?

edited May 23, 2017 at 12:27

CommunityBot

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answered Feb 6, 2012 at 19:39

Bill Karwin

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