Multidimensional Expressions (MDX), the original language of Microsoft SQL Server Analysis Services cubes, is still the industry standard for OLAP (Online Analytical Processing) calculation design, cube querying, and reporting, especially in the world of finance and retail. You will benefit from MDX for many years to come, well into the next decade.
It is not difficult to learn. Let Chris Webb, world’s undisputed authority on MDX, explain it to you. Start by watching the free modules, then purchase access to watch the rest: over 6 hours of video, nearly a hundred demos in this course alone, and the related, SSAS Cube Design course.