MDX calculated measure on dimension value without measure value - mdx

Question

I am new to mdx and SSAS, We are trying to convert our store procedure to mdx query. I have a cube like below:
Fact table：
[Target] (FK),
[Date] (FK),
[Action] (FK),
[Amount] (Measure),
Dim Date:
[DateKey] (pk),
[Date],
[DayOfYear],
[DayofWeek],
[....]
Dim Action: has fourkind of actions (added, removed, connected, ..)
[ID] (PK)
[Name]
Dim Target:
[ID] (PK)
[Name]
I want to create a calculated measure like what we did in t-sql
SELECT ....,
SUM(
CASE
WHEN a.[Action]='added'
THEN DATEDIFF(DAY, a.[Date],GETUTCDATE())
ELSE DATEDIFF(DAY, a.[Date],GETUTCDATE())*-1
END
)/NULLIF( SUM(CASE WHEN a.[Action]='added' THEN 1 ELSE 0 END),0)
AS 'AverageLifespan'
FROM FilterData a
GROUP BY a.[Target]
I have tried following but failed, it only returns 0 ;
With Member [Measures].[LifeSpan] as
CASE
WHEN [Dim Action Types].[Name].CURRENTMEMBER IS [Dim Action Types].[Name].&[added] THEN 1*'datediff("d",[Dim Date].[Date],Now()) '
WHEN [Dim Action Types].[Name].CURRENTMEMBER IS [Dim Action Types].[Name].&[removed] THEN -1*'datediff("d",[Dim Date].[Date],Now()) '
ELSE 0
End
select [Measures].[LifeSpan] on columns,
[Dim Action Targets].[Name].Children on rows
from [OLAP Prep]
-----------output---------------
LifeSpan
tilerecipes/account-news 0
tilerecipes/competitornews 0
tilerecipes/innovation-blog 0
tilerecipes/sales-now 0
tilerecipes/inbox 0
tilerecipes/in-the-news 0
tilerecipes/jobs 0
tilerecipes/l-and-d 0
Tried on below query, still not working (removed the date part, just for testing):
With Member [Measures].[LifeSpan] as
CASE
WHEN [Dim Action Types].[Name].CURRENTMEMBER IS [Dim Action Types]. [Name].&[added] THEN 1
WHEN [Dim Action Types].[Name].CURRENTMEMBER IS [Dim Action Types]. [Name].&[removed] THEN -1
WHEN [Dim Action Types].[Name].CURRENTMEMBER IS [Dim Action Types].[Name].[All] THEN Sum([Dim Action Types].[Name].Children,[Measures].[LifeSpan]) -- this will work.
ELSE 0
End
select [Measures].[LifeSpan] on columns,
[Dim Action Types].[Name].Members on rows
from [OLAP Prep]
--------Output------------
LifeSpan
All 0
added 1
connected 0
disconnected 0
removed -1

Answer 1

There is one thing to remember in MDX : Calculated measures are not aggregated.
When you develop along the [Dim Action Targets].[Name] Axis, the [Dim Action Targets].[Name] default member is used, which is by default [Dim Action Targets].[Name].[All]
If you tried
select [Measures].[LifeSpan] on columns,
[Dim Action Types].[Name].Members on rows
from [OLAP Prep]
You will see your calculated measures behave properly, except for the [Dim Action Types].[Name].[All] Member.
In order for your calculated measure to behave properly on your original request
With Member [Measures].[LifeSpan] as
CASE
WHEN [Dim Action Types].[Name].CURRENTMEMBER IS [Dim Action Types].[Name].&[added] THEN 1*'datediff("d",[Dim Date].[Date],Now()) '
WHEN [Dim Action Types].[Name].CURRENTMEMBER IS [Dim Action Types].[Name].&[removed] THEN -1*'datediff("d",[Dim Date].[Date],Now()) '
WHEN [Dim Action Types].[Name].CURRENTMEMBER IS [Dim Action Types].[Name].[All] THEN Sum([Dim Action Types].[Name].Children,[Measures].[LifeSpan]) -- this will work.
ELSE 0
End
Well, the simplest way would be to create a LifeSpan measure in your cube definition, make it point to your Amount column of your fact table. Let the default behaviour
Now, go to the Calculation tab of the cube definition. Switch to Script mode.
You should see the "CALCULATE" instruction.
CALCULATE;
Scope([Measures].[LifeSpan]);
This = 0; // We zero out the whole thing first
Scope([Dim Date].[Date].Children,[Dim Action Types].[Name].&[added]})
This = datediff("d",[Dim Date].[Date].CURRENTMEMBER,Now())
End Scope;
Scope([Dim Date].[Date].Children,[Dim Action Types].[Name].&[removed]})
This = -datediff("d",[Dim Date].[Date].CURRENTMEMBER,Now())
End Scope;
End Scope;
This measure will aggregate the right way.

Answer 2

You have to use 'MemberValue' like this :
WHEN
[Dim Action Types].[Name].MemberValue IS
[Dim Action Types].[Name].&[added]
THEN
1*'datediff("d",[Dim Date].[Date],Now())