hierarchies and level in SSAS help to improve MDX Query performance?
I use SQL Server 2008 R2 and I use SSAS and I reading book
Professional Microsoft SQL Server Analysis Services 2008 with MDX Wrox Programmer to Programmer
in chapter 5 in page 132 is written that declaring
hierarchies and level make better query performance.
but I do not understand how this works affect in query performance?!?