Question

I need to get the MATCH AGAINST scores from multiple tables with a common key and combine their sums. The goal in the end is to create a search algorithm that will return rows with matching group_IDs. I have built a mysql query that has yet to run without error.

In case you want to know, this is the specific error:

Warning: mysql_fetch_array(): supplied argument is not a valid MySQL
result resource

These are the tables I wish to search:

---

table: jn_groups

group_ID, name

---

table: jn_chat

chat_ID, group_ID, name

---

table: jn_events

event_ID, group_ID, title, description

---

My current query looks like this:

SELECT 
    g.group_ID AS group_ID,
    g.name AS name,
    SUM(gscore + cscore + escore) AS score,
    MATCH(g.name) AGAINST (" . $query . "') AS gscore,
    MATCH(c.name) AGAINST (" . $query . "') AS cscore,
    MATCH(e.title,e.description) AGAINST (" . $query . "') AS escore 
FROM jn_groups g 
LEFT JOIN jn_chat c ON g.group_ID = c.group_ID 
LEFT JOIN jn_events e ON g.group_ID = e.group_ID 
WHERE 
    MATCH(g.name) AGAINST (" . $query . "') 
    OR MATCH(c.name) AGAINST (" . $query . "')
    OR MATCH(e.title,e.description) AGAINST (" . $query . "') 
ORDER BY score

Any help making a query similar to that run would be greatly appreciated!

Answer 1

Two things which could be the reason for breaking this query:

variable $query

All your AGAINST-operators end with "', but start only with ". Make sure $query contains

• valid data and
• start with an '.

Summate the partial results

Your SUM won’t work, because it doesn’t know gscore, cscore and escore. It will look for field names instead. You can change this part of your statement like this (ofc replace hello world with your desired search term):

....
SUM(
    (MATCH(g.name) AGAINST ('hello world'))
    + (MATCH(c.name) AGAINST ('hello world'))
    + (MATCH(e.title,e.description) AGAINST ('hello world'))
) AS score,
....

Two advices:

• Try running the query against your database with a SQL
  tool first (p.e. SQLyog, MySQL Workbench, phpMyAdmin or similar), to see if it is working like you want it to. There are a few other possibilities how to break this (p.e. no or wrong fulltext index definition, wrong field names and such), so you have better control about whats going wrong.
• Be careful when using reserved variables like NAME in field names. Either escape them properly or – in my eyes better – avoid them.