Question

I have a query (below) that takes forever to run when a customer has a lot of categories. I need to speed it up somehow and I can’t figure out how. Any assistance is greatly appreciated.

 SELECT pictures1.*, GROUP_CONCAT(cats_master.categoryName SEPARATOR ';') AS categoryNames
            FROM pictures1
                LEFT JOIN cats_contacts ON pictures1.id =cats_contacts.contact_id
                LEFT JOIN cats_master ON cats_contacts.category_id = cats_master.id
            WHERE pictures1.customer_id = (customer id goes here)
            GROUP BY pictures1.id
            ORDER BY pictures1.l_name ASC

The result of this query is a file that the customer can download – the issue seems to be the category piece.

Answer 1

Having following indexes will greatly speedup the query:

id, l_name, customer_id: pictures table
contact_id: cats_contacts table
id, category_id: cats_master table