We are witnessing an exciting revival of interest in recursive Datalog queries in a variety of emerging application domains such as data integration, information extraction, networking, program analysis, security, and cloud computing. This tutorial brie y reviews the Datalog language and recursive query processing and optimization techniques, then discusses applications of Datalog in three application domains: data integration, declarative networking, and program analysis. Throughout the tutorial, we use LogicBlox, a commercial Datalog engine for enterprise software systems, to allow the audience to walk through code examples presented in the tutorial.