Filtering Tables in DAX
This article describes a number of techniques available to filter tables in DAX, showing possible pitfalls that you can avoid once you know them, in particular using bidirectional filters.
One of the hardest things to do, when learning DAX, is to get rid of common sense reasoning and learn to follow a new set of rules, which are defined in the language and that are somewhat unique. If you come from a previous programming or query language, you tend to map your previous knowledge to DAX, forgetting to follow the simpler path of using just the base rules of the language.