MySQL LEFT JOIN duplicates results

Question

I have a problem with implementing a module where one project can belong to multiple categories. Example: project \"PHP Programmer\" belongs to cat

Answer 1

You can also rewrite this as an "IN" to get around duplicates:

SELECT projects.*
FROM projects      
where projects.id in (select project_id
                      from projects_category
                      WHERE pojects_category.category_id IN (1,3,11)
                     ) and
      projects.id='94'

The "in" prevents duplicates from forming when you are using joins for filtering records.