The Axis0 function expects a tuple set expression for the argument - ssas

Question

I just want to get the invoices distinct count of sales on March. I got this MDX query.
My MDX Query:
select
distinctcount([Measures].[Sales #]) on columns,
--[Measures].[Sales #] on columns,
non empty ([Customer].[Store Group].[Store Group]) on rows
from
(
select
{
[Calendar].[Month].[March 2015]
}
ON columns
from [F1_SalesBI])
But I got the following error, whenever I tried executing this.
Executing the query ...
The Axis0 function expects a tuple set expression for the argument. A string or numeric expression was used.
Execution complete

Answer 1

Here is the definition from msdn:
https://msdn.microsoft.com/en-us/library/ms145519.aspx
Syntax:
DistinctCount(Set_Expression)
You're doing this when you use Measures as the argument:
DistinctCount(Numeric_Expression)
Something like the following should hopefully run ok:
WITH
SET [mySet] AS
[Customer].[Store Group].[Store Group] * {[Measures].[Sales #]}
MEMBER [Measures].[setDistCount] AS
DistinctCount([mySet])
SELECT
{
[Measures].[setDistCount]
,[Measures].[Sales #]
} ON 0
,NON EMPTY
[Customer].[Store Group].[Store Group] ON 1
FROM
(
SELECT
{[Calendar].[Month].[March 2015]} ON 0
FROM [F1_SalesBI]
);
To return the number of invoices for the month try the following:
WITH
SET [mySet] AS
{[Calendar].[Month].[March 2015]} * {[Measures].[Sales #]}
MEMBER [Measures].[setDistCount] AS
DistinctCount([mySet])
SELECT
{
[Measures].[setDistCount]
} ON 0
FROM [F1_SalesBI];
If the above returns 1 then try inspecting the set via this script:
SELECT
{} on 0,
{[Calendar].[Month].[March 2015]} * {[Measures].[Sales #]} ON 0
FROM [F1_SalesBI];
Does this just return 1 member?
How about this (without the set braces around the measure)?:
SELECT
{} on 0,
{[Calendar].[Month].[March 2015]} * [Measures].[Sales #] ON 0
FROM [F1_SalesBI];