What is serious? What is funny? Who is a player? Who is a student? But, most importantly, who is the murderer? Serious games are gaining an ever increasing interest in education and training, and recent studies have used board games as inspirational. This study introduces SQL Murder Mystery, a serious game inspired by the popular board game Cluedo. This game has been designed to assess students' SQL skills and has been tested in a university database management system course during a lab session in which students played in teams. Query logs were examined to explore the behavioural patterns of the teams, by distinguishing different categories of queries: exploratory, focused, review queries, and to relate behaviour with specific SQL learning goals. The analysis revealed that success in the game and fulfilment of SQL learning goals are correlated. In addition, the game helped the instructors to identify the major knowledge gaps of the students, to allow on-time recovery.