Custom site search by category - mysql

Question

I want to create a simple search for a site that I'm working on. I have items in my db that all hold a specific category id and can optionally be linked to multiple tags.
I would like to take whatever search terms come in and query the category.name and tag.name fields to find the items that match those terms.
I'm looking for advice on how to create an efficient/quick query that does this AND orders the results by the items that match closest(most matches)
Here's a quick version of my relevant tables:
item
id | category | title | description
category
id | name | parentId
tag
id | name | uses
item_tag
itemId | tagId

Answer 1

I still didn't entirely understand what you want.
Well, here's a first version for us to discuss.
I suggest you to create a view as the following:
CREATE OR REPLACE VIEW `search_view` AS
SELECT
i.id AS `item_id`,
i.title AS `item_title`,
c.id AS `cat_id`,
c.name AS `cat_name`,
t.id AS `tag_id`,
t.name AS `tag_name`
FROM item AS i
LEFT OUTER JOIN item_tag AS it
ON (i.id = it.itemId)
LEFT OUTER JOIN tag AS t
ON (it.tagId = t.id)
LEFT OUTER JOIN category AS c
ON (i.category = c.id)
WHERE ((t.id IS NOT NULL) OR (c.id IS NOT NULL));
And then you query from the view using something near
SELECT
*,
(
IF(tag_name like ?, 2, 0)
+ IF(cat_name like ?, 4, 0)
+ IF(item_title like ?, 1, 0)
) AS `priority`
FROM search_view
GROUP BY item_id
ORDER BY SUM(priority);
No tests in the code above. Report any problems you have
[first edition] You use PHP, don't you?
Well, you can normalize your queries using PHP string functions; one way is to replace every occurrence of ',' by '|', remove extra spaces and perform the following query: [I'll give an example using #VAR (actually you'll replace it with your input string)]
SET #VAR = 'notebook|samsung';
SELECT
*,
(
IF (tag_name REGEXP CONCAT('.*(', #VAR, ').*'), 2, 0)
+ IF (cat_name REGEXP CONCAT('.*(', #VAR, ').*'), 4, 0)
+ IF (item_title REGEXP CONCAT('.*(', #VAR, ').*'), 1, 0)
) AS `priority`
FROM search_view
ORDER BY priority DESC;
This time I tested. Yes, you can use MySQL functions, something about REPLACE(REPLACE(#VAR,' ',''), ',', '|'). But I recommend you to do it in PHP (or java, python etc).

Answer 2

SELECT item.*
FROM items
LEFT JOIN categories
ON categories.name = '< input name >'
AND categories.id = items.category
LEFT JOIN item_tags
AND item_tags.itemId = items.id
LEFT JOIN tags
ON tags.name = '< input name >'
AND tags.id = item_tags.tagId
WHERE categories.id IS NOT NULL
OR tags.id IS NOT NULL
ORDER BY COUNT(items.id) DESC;
This may not be the fastest way. Basically you'll left join categories and tags to items while making sure the category and tag have the correct name. Filter out all items that don't match a category or an item_tag in the where clause.
Another alternative would be to create temporary tables. Create one for all categories with the correct name, and one with all tags with the correct name. You could then SELECT items WHERE items.id IN categories_table OR items.id IN tags_table