In SQL 2012 DAX became a query language and, when it comes to performance, the xVelocity in-memory engine is second to none. Scanning fact tables and performing leaf-level computation happens in a matter of milliseconds. Nevertheless, as with any other language, you can write good DAX or bad DAX, depending on your understanding of the engine internals. In this session we are going to introduce DAX as a query language, showing the different ways of querying with DAX using real-world data. Some queries will be fast, others will need optimizations and a better understanding of query plans, which we will show, in order to give a complete understanding of how to get the best out of DAX.