This book constitutes the refereed proceedings of the 31th Australasian Database Conference, ADC 2019, held in Melbourne, VIC, Australia, in February 2020. The 14 full and 5 short papers presented were carefully reviewed and selected from 30 submissions. The Australasian Database Conference is an annual international forum for sharing the latest research advancements and novel applications of database systems, data driven applications and data analytics between researchers and practitioners from around the globe, particularly Australia, New Zealand and in the World.