Try this.... just replace "58" below with the appropriate course ID number
SELECT cm.id, cm.course, cm.module, mdl.name AS type,
CASE
WHEN mf.name IS NOT NULL THEN mf.name
WHEN mb.name IS NOT NULL THEN mb.name
WHEN mr.name IS NOT NULL THEN mr.name
WHEN mu.name IS NOT NULL THEN mu.name
WHEN mq.name IS NOT NULL THEN mq.name
WHEN mp.name IS NOT NULL THEN mp.name
WHEN ml.name IS NOT NULL THEN ml.name
ELSE NULL
END AS activityname,
CASE
WHEN mf.name IS NOT NULL THEN CONCAT('/mod/forum/view.php?id=', cm.id)
WHEN mb.name IS NOT NULL THEN CONCAT('/mod/book/view.php?id=', cm.id)
WHEN mr.name IS NOT NULL THEN CONCAT('/mod/resource/view.php?id=', cm.id)
WHEN mu.name IS NOT NULL THEN CONCAT('/mod/url/view.php?id=', cm.id)
WHEN mq.name IS NOT NULL THEN CONCAT('/mod/quiz/view.php?id=', cm.id)
WHEN mp.name IS NOT NULL THEN CONCAT('/mod/page/view.php?id=', cm.id)
WHEN ml.name IS NOT NULL THEN CONCAT('/mod/lesson/view.php?id=', cm.id)
ELSE NULL
END AS linkurl, f.id AS fileid, f.filepath, f.filename, CONCAT('/filedir/', SUBSTRING(f.contenthash, 1, 2), '/', SUBSTRING(f.contenthash, 3, 2), '/', f.contenthash) AS filesystempath, f.userid AS fileuserid, f.filesize, f.mimetype, f.author AS fileauthor, f.timecreated, f.timemodified
FROM mdl_course_modules AS cm
INNER JOIN mdl_context AS ctx ON ctx.contextlevel = 70 AND ctx.instanceid = cm.id
INNER JOIN mdl_modules AS mdl ON cm.module = mdl.id
LEFT JOIN mdl_forum AS mf ON mdl.name = 'forum' AND cm.instance = mf.id
LEFT JOIN mdl_book AS mb ON mdl.name = 'book' AND cm.instance = mb.id
LEFT JOIN mdl_resource AS mr ON mdl.name = 'resource' AND cm.instance = mr.id
LEFT JOIN mdl_url AS mu ON mdl.name = 'url' AND cm.instance = mu.id
LEFT JOIN mdl_quiz AS mq ON mdl.name = 'quiz' AND cm.instance = mq.id
LEFT JOIN mdl_page AS mp ON mdl.name = 'page' AND cm.instance = mp.id
LEFT JOIN mdl_lesson AS ml ON mdl.name = 'lesson' AND cm.instance = ml.id
LEFT JOIN mdl_files AS f ON f.contextid = ctx.id
WHERE cm.course = 58
AND mdl.name = 'resource'
AND ((f.mimetype = 'application/pdf') OR (f.id IS NULL))
NOTE: originally inspired by Darko Miletić solution here: https://moodle.org/mod/forum/discuss.php?d=153059#p1166404