This book constitutes the refereed proceedings of the 30th Australasian Database Conference, ADC 2019, held in Sydney, NSW, Australia, in January/February 2019. The 9 full papers presented together with one demo paper were carefully reviewed and selected from 19 submissions. The Australasian Database Conference is an annual international forum for sharing the latest research progresses and novel applications of database systems, data management, data mining and data analytics for researchers and practitioners in these areas from Australia, New Zealand and in the world.