I recently recorded a screencast that shows how to create an ad-hoc report via TIBCO Jaspersoft Studio for Liferay DXP and it is now available on YouTube. Note that it requires the Liferay Reports Plugin from the Liferay Marketplace. The resulting Jasper Report XML (.jrxml) definition contains an SQL query that performs a join between the AssetEntry and RatingsStats tables in the Liferay database.