Best way to do a weighted search over multiple fields in mysql?

Question

Here\'s what i want to do:

• match a search subject against multiple fields of my table
• order the results by importance of the field and relevance of th

Answer 1

SELECT post_name, post_title,
    (CASE WHEN `post_name` LIKE '%install%' THEN(9 / LENGTH(post_name) * 100) ELSE 0 END) 
    + (CASE WHEN `post_title` LIKE '%install%' THEN(9 / LENGTH(post_title) * 50) ELSE 0 END)
        AS priority
FROM wp_posts
WHERE
    post_title LIKE '%install%'
    OR post_name LIKE '%install%'
ORDER BY priority DESC

This query will not only check weight in columns, but also in each row:

• Checks how important search word is in each field cell. For example install wins over install something if searching for install (length is included in weight calculation).
• Each field can have assigned weights (100 and 50 in this case, optional).

Basically, if we have these values and search for install: (1 column example, but it works with multiple columns too)

• "Something else about install"
• "install"
• "install something"

Search will gives this order:

• "install" - 128 weight
• "install something" - 52 weight
• "Something else about install" - 32 weight

Answer 2

There is a native and clean way to do this using MySQL's CASE function (https://dev.mysql.com/doc/refman/5.7/en/case.html).

Example (untested):

SELECT * FROM `myTable` 
WHERE (`name` LIKE "%searchterm%" OR `description` LIKE %searchterm%" OR `url` LIKE "%searchterm%")
ORDER BY CASE
WHEN `name`        LIKE "searchterm%"  THEN 20
WHEN `name`        LIKE "%searchterm%" THEN 10
WHEN `description` LIKE "%searchterm%" THEN 5
WHEN `url`         LIKE "%searchterm%" THEN 1
ELSE 0
END
LIMIT 20

Have used this for many weighted searches of my own and works an absolute treat!

Answer 3

I had this exact same question and it was fully answered on one of the MySQL forums. Here's the thread. Kind of a long thread (because I'm kind of long-winded) but the payoff is just what you're looking for.

Answer 4

Probably this approach of doing a weighted search / results is suitable for you:

SELECT *,
    IF(
            `name` LIKE "searchterm%",  20, 
         IF(`name` LIKE "%searchterm%", 10, 0)
      )
      + IF(`description` LIKE "%searchterm%", 5,  0)
      + IF(`url`         LIKE "%searchterm%", 1,  0)
    AS `weight`
FROM `myTable`
WHERE (
    `name` LIKE "%searchterm%" 
    OR `description` LIKE "%searchterm%"
    OR `url`         LIKE "%searchterm%"
)
ORDER BY `weight` DESC
LIMIT 20

It uses a select subquery to provide the weight for ordering the results. In this case three fields searched over, you can specify a weight per field. It's probably less expensive than unions and probably one of the faster ways in plain MySQL only.

If you've got more data and need results faster, you can consider using something like Sphinx or Lucene.

Answer 5

you can add multiple mysql MATCH() values together, first multiplying each one by their weight.

simplified of course...

'(MATCH(column1) AGAINST(\''.$_GET['search_string'].'\') * '.$column1_weight.')
 + (MATCH(column2) AGAINST(\''.$_GET['search_string'].'\') * '.$column2_weight.')
 + (MATCH(column3) AGAINST(\''.$_GET['search_string'].'\') * '.$column3_weight.')
 AS relevance'

then

'ORDER BY relevance'

Answer 6

You should use a dedicated indexer to prefetch all of the data into an optimized, searchable index. Sphinx and similar products do this very well.