Question

My mysql query looks like this:

    SELECT pages.*,
           showcase.*,
           project.*    
      FROM pages
INNER JOIN showcase ON showcase.pid = pages.uid AND showcase.deleted != 1
INNER JOIN project ON FIND_IN_SET(project.uid, showcase.projects)   
     WHERE pages.deleted != 1
       AND pages.pid = 14
       AND pages.dokType = 150

The problem is the second INNER JOIN – it uses FIND_IN_SET because a showcase (= collection of projects) stores its projects as a comma separated list in the field showcase.projects. FIND_IN_SET cant use indexes as far as I know, so the second join requires a full table scan of the project table. Any possibility to use an index without changing the database scheme?

Answer 1

You searching for a ‘string’ inside another string. You’ll have to do a scan regardless. The other optimized way to do this using indexes is to use a join table. Create a new table showcase_projects that has columns of project_id and showcase_id. This will then have a record for every association between the two.

Now this answer is based on my primitive understanding of your datastructure from this query.