Returning Top n in DAX and MDX
DAX (Data Analysis eXpressions) and MDX (MultiDimensional eXpressions) are the two main BI (business intelligence) query languages for SSAS (Microsoft SQL Server Analysis Services). For most of the time, these two main query languages (DAX and MDX) can return exactly the same results (at present, MDX has the edge on functionality, so some results are not yet possible in DAX – but this will change in the future). A third BI language, DMX (Data Mining eXtensions) is for more specialised work against an SSAS data mining model. Whether you choose to write queries in DAX or MDX is often a matter of personal preference. You can use both DAX and MDX against an SSAS tabular model, you can also use both against an SSAS multidimensional cube. There is even currently limited support for writing DAX inside MDX!