The custom measure in the following is taken from the book MDX Cookbook (Tomislav Piasevoli):
WITH
MEMBER [Internet Sales PP] AS
Sum
(
Generate
(
{
[Date].[Calendar].[Date].&[20080105]
:
[Date].[Calendar].[Date].&[20080125]
}
,{
ParallelPeriod
(
[Date].[Calendar].[Calendar Year]
,1
,[Date].[Calendar].CurrentMember.Item(0)
)
}
)
,[Measures].[Internet Sales Amount]
)
SELECT
{
[Measures].[Internet Sales Amount]
,[Internet Sales PP]
} ON 0
,[Product].[Color].MEMBERS ON 1
FROM [Adventure Works];
What purpose does the item(0) serve?
My understanding, which is probably wrong is
<set>.item(0) gives us first tuple in set
<tuple>.item(0) gives us first member in tuple
So what is the point of <member>.item(0)?
Refer this excellent article on the topic.
To sum it up, when we are doing a .ITEM(0) on a member, that member is implicitly converted to a tuple. So, .ITEM(0) does not really serve any purpose other than returning the member itself.
I would assume this is a typo or a copy paste error. At least in the official Microsoft MDX reference, there are only the two Item() versions that you mention.
And this does not cause an error, as there are some implicit type conversions:
If you have a member and need a tuple for the current expression, AS implicitly builds a one-member tuple from the member. Which is what takes place here presumably, when applying Item(0) to a member.
If you have a one member tuple and need a member for the current expression, AS implicitly applies Item(0).
There are similar implicit conversions from tuple and level to set, from tuple to scalar value, from dimension to hierarchy, and from hierarchy to member.
Related
Here are two simple queries which shows data on month level filtered by dates.
In the first query I am using Month level of "Date.Calendar" user hierarchy.
SELECT
NON EMPTY { [Measures].[Internet Sales Amount] } ON 0,
NON EMPTY { [Date].[Calendar].[Month].&[2013]&[1] } ON 1
FROM [Adventure Works]
WHERE {[Date].[Date].&[20130105]:[Date].[Date].&[20130106]}
And recieved - January 2013 -> $857,689.91
Results
In the second query I am using "Date.Month of Year" attribute hierarchy.
SELECT
NON EMPTY { [Measures].[Internet Sales Amount]} ON 0,
NON EMPTY { [Date].[Month of Year].&[1] } ON 1
FROM [Adventure Works]
WHERE { [Date].[Date].&[20130105] : [Date].[Date].&[20130106] }
And received - January -> $54,468.46
Results
I can not figure out why these two queries show different results. If the same dimension is used and data are filtered/sliced on the lovest possible level.
Here are values for each of these dates.
SELECT
NON EMPTY { [Measures].[Internet Sales Amount]} ON 0,
NON EMPTY { [Date].[Calendar].[Date] } ON 1
FROM [Adventure Works]
WHERE { [Date].[Date].&[20130105] : [Date].[Date].&[20130106] }
January 5, 2013 $32,681.44
January 6, 2013 $21,787.02
Result
Total value for these two dates is equal with the second querie's result - $54,468.46
I understand that in the first query it is user hierarchy and the second query it is attribute hierarchy from the Date dimension but I can not figure out which rule(s) tells to calculate these values differently.
If someone could explain this logic behind - it would be very helpful. Any link to some resource which explains this logic also could help.
BTW: I have created simple cube with simple Date dimension which consists just of attribute hierrarchies (date, month, year) and it still works like in the first query so it is not clear why it behaves like that.
I explored the reason for this behavior, and I think I have figured out the reason. The explanation below is based on the book SQL SERVER 2008 MDX Step by Step pages 51-58(especially Avoiding Reference Conflicts).
Your problem is a typical Reference Conflict problem.In MDX a hierarchy cannot be used more than once in a given tuple, but if you are using a USER Hierarchy and its under lying Attribute Hierarchy, you essentially by-pass this check. This is what happened in your query
In your first query you are using the User Hierarchy
[Date].[Calendar].[Month].&[2013]&1
In MDX a User Hierarchy is translated to Attribute Hierarchies. In your first query
SELECT
NON EMPTY { [Measures].[Internet Sales Amount] } ON 0,
NON EMPTY { [Date].[Calendar].[Month].&[2013]&1 } ON 1
FROM [Adventure Works] WHERE
{[Date].[Date].&[20130105]:[Date].[Date].&[20130106]}
you are using a User Hierarchy "[Date].[Calendar].[Month].&[2013]&1", which in its last level has "[Date].[Date]". Then in the where clause you use the same "[Date].[Date]" Attribute Hierarchy to filter. Since in the USER Hierarchy you have not used the leaf level, hence you have made a partial address, therefore the members and its ancestors are resolved. All the descendants are ignored in translation. Take a look at the below query(This is based on your first query,I have purposely removed your where clause).
with member [Measures].[CalendarYear] as [Date].[Calendar Year].currentmember.name
member [Measures].[CalendarSemester] as [Date].[Calendar Semester of Year].currentmember.name
member [Measures].[CalendarQuater] as [Date].[Calendar Quarter of Year].currentmember.name
member [Measures].[CalendarMonth] as [Date].[Month of Year].currentmember.name
member [Measures].[CalendarDate] as [Date].[Date].currentmember.name
SELECT
NON EMPTY { [Measures].[Internet Sales Amount] ,[Measures].[CalendarYear],[Measures].[CalendarSemester],[Measures].[CalendarQuater],[Measures].[CalendarMonth],[Measures].[CalendarDate]} ON 0,
NON EMPTY { [Date].[Calendar].[Month].&[2013]&[1] } ON 1
FROM [Adventure Works]
Result.
Notice that Calendar year, Semester and quarter all are showing non-default values. But we never used them. This shows that translation of User Hierarchy is done into underlying Attribute Hierarchies. Now take a look at Calendar, it is still showing "All Period". Since it was ignored.
Now if you add your where clause back, the Date still shows "All Period", there are two reasons
1) Because it was ignored in User Hierarchy translation ,
2)You used a range in where. If you replace your row axis tuple with your where tuple it will still show "All Period" as a range is based. However while resolving it will take just two dates.
Based on this while resolving your query, it had two translation for Date attribute hierarchy, one said to ignore it based on User Hierarchy, the other provided a range. This is where due to conflict the result is in-correct.
Now lets consider the query you gave me in your comment earlier
with member [Measures].[CalendarYear] as [Date].[Calendar Year].currentmember.name
member [Measures].[CalendarSemester] as [Date].[Calendar Semester of Year].currentmember.name
member [Measures].[CalendarQuater] as [Date].[Calendar Quarter of Year].currentmember.name
member [Measures].[CalendarMonth] as [Date].[Month of Year].currentmember.name
member [Measures].[CalendarDate] as [Date].[Date].currentmember.name
SELECT
NON EMPTY { [Measures].[Internet Sales Amount] ,[Measures].[CalendarYear],[Measures].[CalendarSemester],[Measures].[CalendarQuater],[Measures].[CalendarMonth],[Measures].[CalendarDate]} ON 0,
NON EMPTY { [Date].[Calendar].[Month].&[2013]&[1] } ON 1
FROM [Adventure Works]
WHERE {[Date].[Date].&[20130105]}
Result:
Notice that this time the resolution of a single member, was used instead of the User hierarchy resolution. Now this behavior might be due to the fact that one translation is giving "All Period" and the next is giving a member, hence the member won.
To further confirm this, I made a change to my AdventureWorks sample. The Date attribute hierarchy is based on "Simple Date" column. I exposed "Simple Date" as a separate attribute and processed my cube.
Take a look at the "Simple Date" query and results.
with member [Measures].[CalendarYear] as [Date].[Calendar Year].currentmember.name
member [Measures].[CalendarSemester] as [Date].[Calendar Semester of Year].currentmember.name
member [Measures].[CalendarQuater] as [Date].[Calendar Quarter of Year].currentmember.name
member [Measures].[CalendarMonth] as [Date].[Month of Year].currentmember.name
member [Measures].[CalendarDate] as [Date].[Date].currentmember.name
SELECT
NON EMPTY { [Measures].[Internet Sales Amount] ,[Measures].[CalendarYear],[Measures].[CalendarSemester],[Measures].[CalendarQuater],[Measures].[CalendarMonth],[Measures].[CalendarDate]} ON 0,
NON EMPTY { [Date].[Calendar].[Month].&[2013]&[1] } ON 1
FROM [Adventure Works]
WHERE
--{[Date].[Date].&[20130105]}
{[Date].[Simple Date].&[20130105]:[Date].[Simple Date].&[20130106]}
Results:
I understand how to use the MDX Aggregate() and Sum() functions, and the differences between them.
(One interesting one is that the Sum of a measure defined at a higher level in a hierarchy over that level's Children multiplies the measure by the number of children - whereas Aggregate "correctly" returns just the value defined at the higher level).
The documented syntax on MSDN is:
Aggregate(Set_Expression [ ,Numeric_Expression ])
I've always used it with both arguments. But what does Aggregate do when only the set_expression argument is provided? The documentation (again from MSDN) is pretty obscure:
If a numeric expression is not provided, this function aggregates each measure within the current query context by using the default aggregation operator that is specified for each measure.
I tried it in an MDX query like this:
WITH MEMBER WeekSummedTotal AS
Aggregate([Days].[WeeksAndDays].CurrentMember.Children)
SELECT
{Measures.ThingoCount,Measures.WeekTotal,Measures.WeekSummedTotal} ON 0,
[Days].[WeeksAndDays].[WeekName] ON 1
FROM DateGRoupingTest
What would this do? Would Aggregate aggregate the cube's default measure over the set? Or the set Measures.Members? Or the set of other measures specified on the 0 axis?
None of these! The query runs and returns results, but the calcd measure WeekSumTotal shows #Error, with a completely nonsensical error:
Aggregate functions cannot be used on calculated members in the measures dimension
Now this is true, but completely irrelevant. None of the other measures in the query is calculated, and in fact the cube doesn't have any calculated members. So what is Aggregate() actually trying to do here? Is this error message (again, in MDX!) completely misleading?
ADDITION: #whytheq in the answer below suggested creating the calculated measure using Aggregate, but creating it on a spare dimension hierarchy rather than in the Measures dimension. This works, but only if the cross-join with the [All] member of the selected "any old..." dimension is included.
Creating the measure there also makes it impossible to put the two (base) measures and the calculated measure on the same axis. If I try to do this:
{Measures.ThingoCount,Measures.WeekTotal,[Ages].[Age Key].WeekSummedTotal} ON 0,
I get the deeply-unhelpful error message:
Members, tuples or sets must use the same hierarchies in the function.
which, I think, translates to "I can't make a set using the , (UNION) function between members of Measures and members of [Ages].[Age Key] because they're members of different dimensions".
My conclusion, thanks to your informative answers, is that Aggregate() with a single argument is a tricky beast; I wonder why it was designed with the second argument optional?
I've also noted that trying to create my calculated member on my Ages dimension (only one hierarchy, only one attribute) gives me the misleading error message:
The 'Ages' dimension contains more than one hierarchy, therefore
the hierarchy must be explicitly specified.
unless I explicitly specify the hierarchy. MDX has so much potential, but the learning curve would be that much gentler if MS had put more effort into making it feed back errors properly.
What would this do? Would Aggregate aggregate the cube's default
measure over the set? Or the set Measures.Members? Or the set of other
measures specified on the 0 axis?
Aggregate function aggregates the set over the current measure for Measures dimension. And a measure is "current" if it is in scope. If a measure is not in scope, the default member from measures dimension is considered for aggregation.
A measure can be added to scope in many ways like
Having the measure on axes
with member [Customer].[Customer].abc as
aggregate([Customer].[Customer].members)
select [Customer].[Customer].abc on 0,
{[Measures].[Internet Sales Amount],[Measures].[Reseller Sales Amount]} on 1
from [Adventure Works]
In the above example the member abc was calcualted twice, once for each measure.
Using Subcube
with member [Customer].[Customer].abc as
aggregate([Customer].[Customer].members)
select [Customer].[Customer].abc on 0
from (select {[Measures].[Internet Sales Amount] } on 0 from [Adventure Works])
Having the measure in definition
with member [Customer].[Customer].abc as
aggregate([Customer].[Customer].members, [Measures].[Internet Sales Amount])
select [Customer].[Customer].abc on 0
from [Adventure Works]
In Where clause
with member [Customer].[Customer].abc as
aggregate([Customer].[Customer].members)
select [Customer].[Customer].abc on 0
from [Adventure Works]
where [Measures].[Internet Sales Amount]
As suggested by whytheq, have the member on some other dimension-hierarchy combo. Otherwise, the aggregate function would probably lead to the calculated member self-referencing itself.
Taking this section of the MSDN definition:
...this function aggregates each measure within the current query
context ...
each measure in the context of your script is the following:
{Measures.ThingoCount,Measures.WeekTotal,Measures.WeekSummedTotal}
Now Measures.WeekSummedTotal is a calculated members in the measures dimension - hence the error.
I'd imagine something like the following would function ok, where you use Aggregate to create a member in a dimension other than Measures?:
WITH
MEMBER [SomeSpareDim].[SomeSpareHier].WeekSummedTotal AS
Aggregate
(
[Days].[WeeksAndDays].CurrentMember.Children * [SomeDim].[SomeHier].[All]
)
SELECT
[SomeSpareDim].[SomeSpareHier].WeekSummedTotal ON 0
,[Days].[WeeksAndDays].[WeekName] ON 1
FROM DateGRoupingTest;
The above can be changed to show Aggregate being very useful:
WITH
MEMBER [Days].[WeeksAndDays].[Last3Weeks] AS
Aggregate
(
{
[Days].[WeeksAndDays].[Weekx]
,[Days].[WeeksAndDays].[Weeky]
,[Days].[WeeksAndDays].[Weekz]
}
)
SELECT
{Measures.ThingoCount,Measures.WeekTotal} ON 0
,{
//<< the following custom aggregated member will work for any measure, that is ON 0, via Aggregate
//it can be mixed up with the normal members of the same hierarchy like the following
[Days].[WeeksAndDays].[Last3Weeks]
,[Days].[WeeksAndDays].[WeekName].members
} ON 1
FROM DateGRoupingTest;
The following script gives exactly the result I want.
It feels like a hack as I've added the custom members VALUE and VALUE_MTD onto the hierarchy [Customer].[Country]. I've chosen this hierarchy arbitrarily - just not used [Measures] or [Date].[Calendar] as they are already in use.
Is there a more standard approach to returning exactly the same set of cells?
WITH
MEMBER [Customer].[Country].[VALUE] AS
Aggregate([Customer].[Country].[(All)].MEMBERS)
MEMBER [Customer].[Country].[VALUE_MTD] AS
Aggregate
(
PeriodsToDate
(
[Date].[Calendar].[Month]
,[Date].[Calendar].CurrentMember
)
,[Customer].[Country].[VALUE]
)
SELECT
{
[Customer].[Country].[VALUE]
,[Customer].[Country].[VALUE_MTD]
} ON 0
,NON EMPTY
{
[Measures].[Internet Sales Amount]
,[Measures].[Internet Order Quantity]
}
*
Descendants
(
{
[Date].[Calendar].[Month].&[2007]&[12]
:
[Date].[Calendar].[Month].&[2008]&[01]
}
,[Date].[Calendar].[Date]
) ON 1
FROM [Adventure Works];
The standard approach is called utility dimension. If you Google this term, you will find several descriptions of this approach. A "utility dimension" is one which does not reference any data, but is just added to the cube for the purpose of being able to cross join them with all other dimensions for calculations. You can have one or more of them.
Thus, in most cases, physically there is nothing in the dimension. It is just used for calculated members. (Depending on the implementation, you may have the attribute members defined physically, if you want to have some properties for them. But then, only the default member is referenced in the star schema from the fact tables. The attribute member values are then overwritten in the calculation script.)
Typical applications for this are time calculations like YTD, MTD, MAT (Moving Annual Total, i. e. a full year of data ending in the selected date), or comparisons like growth vs. a previous period.
I am attempting to return a measure two periods from the current member on the time dimension however I need to only include periods that match a certain criteria (Is_Business_Day = true)
I currently have:
(
[Date].[Calendar].CURRENTMEMBER.NEXTMEMBER.NEXTMEMBER,
[Measures].[SOME MEASURE]
)
Which accurately returns the value of the measure two members in the future, but now I need to additionally apply the filter, but can't quite figure out how to do so.
EDIT:
My thinking is that I would have to do something similar to the following
(
Head(
exists(
[Date].[Calendar].CurrentMember.NextMember:[Date].[Calendar].CurrentMember.Lead(6),
[Date].[Is Business Day].&[True]
),
2
).item(1),
[Measures].[SOME MEASURE]
)
As both hierarchies, [Date].[Calendar] and [Date].[Is Business Day] are in teh same dimension, you can rely on SSAS "Autoexists" which is usually faster than Exists. Hence,
((([Date].[Calendar].[Date].&[20050718].nextmember : null )
*
{ [Date]..Item(0) }
).Item(0)
,[Measures].[SOME MEASURE]
)
The : null construct builds a set to the end of the Date level, i. e. to the last day contained in the attribute.
Cross joining with [Date].[Is Business Day].&[True] automatically restricts the set to those members that co-exist in the dimension (the magic of autoexists).
And .Item(0) extracts the first tuple. In case you need a tuple not of the date, the .Item(0), and the measure member, but just of the date and the measure in your context, apply another Item(0) after the first. This would extract the first member from the tuple.
I am using Performance Point Dashboard Designer 2013 and SharePoint Server 2013 for building dashboards. I am using SSAS2012 for Cube.
I have a scenario similar to the one illustrated by figure below. I am required to find Previous Non-Empty value for purpose of finding Trends.
Measure: [Quota]
Dimension: [Date].[Calendar Date].[Date]
The script ([Measures].[Quota], [Date].[Calendar Date].PrevMember) gives you a previous date. Lets say for date 27-Jan-13 whose Quota value is 87, it returns 26-Jan-13 which has null value. I want it to return 21-Jan-13 that has some Quota value. And for date 21-Jan-13, I want to return 15-Jan-13.
I wonder if this is possible.
Thanks,
Merin
After long searches and hits & trials and so on, I think I invented a solution of my own for myself.
Following is the script for my Calculated Member.
(
[Quota],
Tail
(
Nonempty
( LastPeriods(15, [Date].[Calendar Date].PrevMember)
,[Quota]
)
).Item(0)
)
Explanation
The number 15 means it will look for non-empty measures up to 15 siblings.
Now we know up to how many siblings to traverse back, in this case 15.
Lets find 15 previous siblings (both empty and non-empty) excluding current member.
(LastPeriods(15, [Date].[Calendar Date].PrevMember)
Since it will yield both empty and non-empty members, lets filter out empty members in terms of measure [Quota]. If we don't specify measure here, it will use default measure whatever it is and we may not get desired result.
Nonempty(LastPeriods(15, [Date].[Calendar Date].PrevMember),[Quota])
We may have several members in the output. And we will choose the last one.
Tail
(
Nonempty
( LastPeriods(15, [Date].[Calendar Date].PrevMember)
,[Quota]
)
)
So far, the script above gives previous non-empty member. Now we want to implement this member for our measure [Quota].
Hence we get the script below ready to create a Calculated Member.
(
[Quota],
Tail
(
Nonempty
( LastPeriods(15, [Date].[Calendar Date].PrevMember)
,[Quota]
)
).Item(0)
)
You can use recursion to define this.
The following query delivers something similar for the Adventure Works cube:
WITH member [Measures].[Prev non empty] AS
IIf(IsEmpty(([Date].[Calendar].CurrentMember.PrevMember, [Measures].[Internet Sales Amount])),
([Date].[Calendar].CurrentMember.PrevMember, [Measures].[Prev non empty]),
([Date].[Calendar].CurrentMember.PrevMember, [Measures].[Internet Sales Amount])
), format_String = '$#,##0.00'
SELECT {[Measures].[Internet Sales Amount], [Measures].[Prev non empty]}
ON COLUMNS,
non empty
Descendants([Date].[Calendar].[Month].&[2007]&[12], [Date].[Calendar].[Date])
ON ROWS
FROM [Adventure Works]
WHERE [Customer].[Customer].&[12650]
You would have to replace the name of the date hierarchy, as well as the measure name from Internet Sales Amount to Quota in the recursive definition of the measure Prev non empty.