If your SSRS report is using SSAS MDX datasets, the member uniquename is particularly useful to pass parameter values to drill-through MDX reports or for sorting based on key values. If Fields!Attribute.UniqueName is returning nothing or blank or null value in your report, then most likely you are missing the DIMENSION PROPERTIES clause in your MDX dataset query
This is most likely to happen with hand written MDX queries rather than those generated by the query designer where the DIMENSION PROPERTIES clause is included by default. Just include DIMENSION PROPERTIES MEMBER_CAPTION, MEMBER_UNIQUE_NAME to your hand written MDX queries to correct this.
SELECT [Measures].[Internet Sales Amount] ON COLUMNS,
(Filter([Date].[Fiscal Year].Children,[Measures].[Internet Sales Amount] > 0),
[Sales Territory].[Sales Territory Country].children,
DIMENSION PROPERTIES MEMBER_CAPTION, MEMBER_UNIQUE_NAME
FROM [Adventure Works]
You could also include MEMBER_KEY to the DIMENSION PROPERTIES clause to get the key value of the attribute if it’s different from the attribute’s name column.
@BennyAustin Always hilarious when you search for a solution and find it on your own blog 🙂 Oh, and MDX is the devil's work.—
Scott Senkeresty (@ScottSenkeresty) August 07, 2015