Fix my Moodle sql query

I need the help from a SQL expert. When I execute the following query I get most of the information I want, that is full completed courses by user in Moodle. The problem is when I add one course column to be shown as a result, for example [login to view URL], records start being duplicated. I suppose it is due to one of my JOIN but I've tried moving them without find the problem. Thank you. SELECT username, FROM_UNIXTIME([login to view URL], '%d-%m-%Y') AS date_created, [login to view URL] FROM mdl_user u JOIN mdl_customcert_issues ON [login to view URL] = [login to view URL] JOIN mdl_user_enrolments ue ON [login to view URL] = [login to view URL] JOIN mdl_enrol e ON [login to view URL] = [login to view URL] JOIN mdl_role_assignments ra ON [login to view URL] = [login to view URL] JOIN mdl_context ct ON [login to view URL] = [login to view URL] AND [login to view URL] = 50 JOIN mdl_course c ON [login to view URL] = [login to view URL] AND [login to view URL] = [login to view URL]