Issue with SSAS: Definition of a set causes a circular reference - ssas

Question

This is ok and returns the sum of the default measure for the past 30 days:
SELECT
FROM [OurCube]
WHERE (
closingperiod(
[Date].[Date - Calendar Month].[Calendar Day],
[Date].[Date - Calendar Month].defaultmember
):
closingperiod(
[Date].[Date - Calendar Month].[Calendar Day],
[Date].[Date - Calendar Month].defaultmember
).ITEM(0).LAG(30)
)
How do I transfer the set of dates in the WHERE clause into the WITH clause ?
I attempted the following but it creates the error message detailed:
WITH
SET [30Days] AS
{
closingperiod(
[Date].[Date - Calendar Month].[Calendar Day],
[Date].[Date - Calendar Month].defaultmember
):
closingperiod(
[Date].[Date - Calendar Month].[Calendar Day],
[Date].[Date - Calendar Month].defaultmember
).ITEM(0).LAG(30)
}
SELECT
FROM [OurCube]
WHERE (
[30Days]
)
Executing the query ...
The definition of the 30Days set contains a circular reference.
Execution complete

Answer 1

I believe this is a limitation of SSAS and has something to do with the execution processing of the different parts of the query; even using a SUB-QUERY (i.e., FROM ( SELECT ... )) instead of a WHERE would not solve the issue.
You can define your set at schema level :
CREATE STATIC SET [OurCube].[30Days] as ...
Or depending on your client application at session level:
CREATE SESSION STATIC SET SET [OurCube].[30Days] as ...