Why am I getting duplicate results in my query?

I am using the Moodle database to query the latest forum posts made by students and teachers for the relevant course they are enrolled in. Here are the tables I need to join and an explanation in what they hold: >mdl_forum_posts = "all posts are stored in this table" mdl_forum_discussions = "forums are composed as discussions" mdl_user = "information stored about users" mdl_log = "activity of every user of the system be it, log in - adding a post" mdl_user_enrolments = "users participating in courses" mdl_enrol = "instances of enrolment plugins used in mdl_course" mdl_course = "courses available in the system" Here is my query: SELECT l.time AS TimeofPost, l.action as Action, usr.id as UserID, usr.firstname,usr.lastname, c.id as CourseID , c.fullname, c.idnumber, fd.name, fd.timemodified as CreatedOn, fp.created, fp.modified, fp.subject, fp.message FROM mdl_forum_posts fp LEFT JOIN mdl_forum_discussions fd ON fp.discussion = fd.id LEFT JOIN mdl_user usr ON fp.userid = usr.id LEFT JOIN mdl_log l ON usr.id = l.userid LEFT JOIN mdl_user_enrolments ue ON usr.id = ue.userid LEFT JOIN mdl_enrol e ON ue.enrolid = e.id LEFT JOIN mdl_course c ON e.courseid = c.id WHERE (action = 'add post' OR action = 'add discussion') The problem I have is that I am getting duplicate results.