If you want to use the MDX query language to work with OLAP cubes like Kognitio, Microsoft Analysis Services, Oracle OLAP Option, SAP BW, SAP HANA, or Teradata OLAP, you really need a good background on how to use the language.  One of the world experts on the MDX query language is Chris Webb and he has produced a very nice little video tutorial on the MDX query language.  You can click here to see his video on MDX Query Language Concepts.  Note that this video is targetted at Microsoft Analysis Services but the MDX query language concepts actually carry over to pretty much ever MDX server out there.