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Archive for November, 2014

MDX #45–Find all the Calculated Sets and Their Calculation Scripts

November 14, 2014 Leave a comment

Now we know how to find all the calculation scripts in a cube by querying the DMV $SYSTEM.MDSCHEMA_MEASURES.

MDX #43–Find a MDX Calculation Script

What about all those calculated sets in the cube?

In the Adventure Works cube, there are quite many calculated sets scattered around in the Sets folder in some dimensions, as shown in the following screenshot.

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How do we find out all of them and their calculation scripts using the DMVs?

Now this time we can use this DMV $SYSTEM.MDSCHEMA_SETS.

SELECT * FROM    $SYSTEM.MDSCHEMA_SETS

Here is the result. The EXPRESSION field shows the calculation scripts.

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Categories: MDX Challenges Tags: ,

MDX #44–How to find all the calculated measures

November 13, 2014 Leave a comment

Calculated measures are visually identifiable

If you have access to a cube, it’s quite easy to find all the calculated measures.

The following is a screenshot from SSMS MDX query editor. The icon next to each measure can visually tell you if it’s a regular measure or a calculated measure. The icon with three uneven bars indicates a regular measure, and the one with a calculator and an orange bar (not sure what it represents) on top indicates a calculated measure.

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AllMembers function returns both the regular and calculated measures

I am always interested in knowing how to also accomplish things with MDX queries.

It turned out it’s pretty simple. The key is the AllMembers function.

By default, MDX excludes calculated members when it resolves set functions. In this blog, I am only examining the special dimension, Measures, which has only one single visible hierarchy; as a result, the hierarchy can be either referred to by the dimension name or by the hierarchy name. So both of the following are valid expressions, and both will return regular measures only.

[Measures].[Measures].Members
[Measures].Members

The AllMembers function is very straightforward. It will return what it is meant to do, both the regular measures and the calculated measures.

Here are 4 simple statements regarding how to use AllMembers function to get calculated measures.

  1. Members function only returns regular members, or regular measures on the Measures hierarchy.
  2. AllMembers function returns regular members AND calculated members, or calculated measures on the Measures hierarchy.
  3. (AllMembers – Members) gives us calculated measures only.
  4. AddCalculatedMembers() function is semantically similar to the AllMembers function.

The following are 4 MDX queries to demonstrate the 4 statements above.

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The following screenshot shows the results.

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Here are the queries in text.

–1. Members function only returns regular members, or regular measures on the Measures hierarchy
SELECT
{[Measures].Members} ON COLUMNS
FROM
[Adventure Works]
go

–2. AllMembers function returns regular members AND calculated members, or calculated measures on the Measures hierarchy
SELECT
{[Measures].AllMembers} ON COLUMNS
FROM
[Adventure Works]
go

–3. AllMembers – Members gives us calculated measures only
SELECT
{ [Measures].AllMembers –
[Measures].Members
} ON COLUMNS
FROM
[Adventure Works]
go

–4. AddCalculatedMembers() function is the same as the AllMembers function
SELECT
AddCalculatedMembers([Measures].Members) –
[Measures].Members
ON COLUMNS
FROM [Adventure Works]

The AllMembers function and the AddCalculatedMembers() function can be also applied to other regular dimensions to get the calculated members.

MDX #43–Find a MDX Calculation Script

November 12, 2014 Leave a comment

Finding out MDX calculation scripts is a common task

A co-worker recently asked me what the calculation for a calculated measure is in our reporting cube.

If you have the Analysis Services project in Visual Studio locally, it is easy to find what the calculation script is from the Calculations tab in the cube designer.

But what if you don’t have the VS project handy, and you have access to the cube from SQL Server Management Studio?

EXPRESSION field in $SYSTEM.MDSCHEMA_MEASURES

Here is a simple script you can run to quickly get the calculation script.

This script queries the SSAS Dynamic Management View $SYSTEM.MDSCHEMA_MEASURES. The EXPRESSION field will return the actual calculation script. You will need to run the DMV queries in the MDX query editor, not the SQL query editor.

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Here is the result.

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Here is the query in text.

SELECT    CUBE_NAME
,        MEASURE_UNIQUE_NAME
,        EXPRESSION
,        MEASUREGROUP_NAME
from    $SYSTEM.MDSCHEMA_MEASURES
where    MEASURE_UNIQUE_NAME = ‘[Measures].[Ratio to Parent Product]’

Use $SYSTEM.DBSCHEMA_COLUMNS to find all the columns in a DMV

You might ask how do I know what are all the columns in this view. Here is a DMV view, $SYSTEM.DBSCHEMA_COLUMNS, you can query to find out all the columns in a DMV view.

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Here is the result.

 

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Here is the query in text.

SELECT *
FROM    $SYSTEM.DBSCHEMA_COLUMNS
WHERE    TABLE_SCHEMA = ‘$SYSTEM’
AND        TABLE_NAME = ‘MDSCHEMA_MEASURES’

$SYSTEM.DISCOVER_SCHEMA_ROWSETS is the only DMV name you need to remember

You might also ask how would I know to use the view $SYSTEM.MDSCHEMA_MEASURES to find out the calculation script.

The answer is to just remember one view, $SYSTEM.DISCOVER_SCHEMA_ROWSETS.

SELECT * FROM $SYSTEM.DISCOVER_SCHEMA_ROWSETS

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The $SYSTEM.DISCOVER_SCHEMA_ROWSETS view will show you all the DMV views that you can use to get the metadata about your dimensions and cubes.

 

DMVs can be very useful for documenting SSAS databases, monitoring usage and activity. To know more about how to use these DMVs check out our book “MDX with SSAS 2012 Cookbook”.

Categories: MDX Challenges, SSAS Tags: , ,

MDX #42–IsEmpty? or = 0 ? or IS NULL?

November 12, 2014 2 comments

In SQL, NULL means undefined value

Any SQL programmer can tell you that zero is not NULL, NULL is not zero, and NULL is not even equal to NULL either, because NULL means undefined. One undefined value cannot be equal to another undefined value.

In MDX, NULL means an empty cell

What about in MDX, how do we detect zero and NULL? What does even NULL mean? Since we are leaving the one dimensional SQL world, and are stepping into the multi-dimensional cube, NULL has a slightly different meaning. To me, it really means an empty cell. When the Internet Sales is showing as (null) for 11/11/2014, it means that the cell of {[Internet Sales], [11/11/2014]} is an empty cell. If you query the fact table, SELECT Internet Sales FROM factSales WHERE Date = 11/11/2014, it should return no rows back.

What if the Internet Sales is showing as 0 (zero) for 11/11/2014? The cell is no longer empty. the fact table should have one row WHERE Date = 11/11/2014, only that the Internet Sales is zero.

Detecting zero and NULL in MDX

How do we detect when Internet Sales is zero or when the cell is totally empty in MDX?

I wrote the following demo MDX code to see the various ways and the results.

I first created two values, a zero value and a NULL value.

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Then I created three new values to detect the zero value, using three different ways

  • 0 = 0?: is 0 = 0?. It should be true.
  • 0 Is NULL?: It should be false.
  • 0 IsEmpty?: It should be false.

 

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I also created three new values to detect the NULL value, using three different ways

  • NULL = 0?: a big question mark here.
  • NULL Is NULL?: It should be false. Remember NULL is not equal to NULL in SQL.
  • NULL IsEmpty?: It should be true. Remember NULL means empty cell in MDX.

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Then I wrote the following MDX query.

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Here is the result.

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Zero is zero, AND NULL is also zero

Do the four results in red surprise you?

  • Zero is zero, AND NULL is also zero.
  • Zero is certainly not empty.
  • NULL IS empty.

It did surprise me. I don’t have much explanation why MDX thinks NULL is zero. At this point, I am just taking in this fact.

Here is the code in text.

with
member [measures].[A Zero Value] as 0
member [measures].[A NULL Value] as null

member [measures].[0 = 0?] as
iif ( [measures].[A Zero Value] = 0,
“true”,
“false”
)
member [measures].[0 Is NULL?] as
iif ( [measures].[A Zero Value] is null,
“true”,
“false”
)
member [measures].[0 IsEmpty?] as
iif ( IsEmpty([Measures].[A Zero Value]) = True,
“true”,
“false”
)
member [measures].[NULL = 0?] as
iif ( [measures].[A NULL Value] = 0,
“true”,
“false”
)
member [measures].[NULL Is NULL?] as
iif ( [measures].[A NULL Value] is null,
“true”,
“false”
)
member [measures].[NULL IsEmpty?] as
iif ( IsEmpty([Measures].[A NULL Value]) = True,
“true”,
“false”
)

select { [Measures].[A Zero Value],
[measures].[0 = 0?],
[measures].[0 Is NULL?],
[measures].[0 IsEmpty?],
[Measures].[A NULL Value],
[measures].[NULL = 0?],
[measures].[NULL Is NULL?],
[measures].[NULL IsEmpty?]
} on 0
from    [RADM_REPORTING]

Empty cells, natural or user-defined can be a powerful way to optimize our MDX queries

Then you might think that since MDX thinks NULL is zero, then why many people set certain side of a MDX calculation to be NULL. Why cannot we all use zero, not mess with the NULL? Well, empty cells, natural or user-defined can be a powerful way to optimize our MDX queries, with the help of either the NONEMPTY() function or the Non EMPTY keyword that works only axes. Check out our book MDX with SSAS 2012 Cookbook on this topic.

Categories: MDX Challenges Tags: ,

SSRS #75 – Use RunningValue() Function and VB Script to capture discrete dates

November 11, 2014 Leave a comment

Drill-down report is a common design

In SSRS, it’s a common design to allow users to drill down to more granular data in a same report.

In the following snapshot, users will see a summary line that shows the Call Handled 130. The two days, 11/4 and 11/5 will not be immediately visible. Only when the user clicks the + sign in the All Dates field, the two detail lines will become visible. All this is happening in the same report.

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Result set can contain only discrete dates

In this particular report, I had two date filters, as shown below.

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The date filters ask for data in a continuous date range, starting from 11/1 to 11/10. However, the report is only showing some discrete dates per employee. This is because other filters suppress certain dates.

The point here is that although the date filters ask for data in a continuous date range, the result set contains only discrete dates within the date range.

Now the users ask you to create a hyperlink to go to a separate report, to show data for that employee, and for those discrete dates only.

The challenge becomes how do we capture those discrete dates within a group (The report is grouped by employee).

Capture discrete dates in SSRS

You might attempt to create a stored procedure to run the same query for the current report again so you can capture those discrete dates in your code, and then pass them to your second query to get the new report.

This will not be my first choice though, because it requires a lot of coding, not mention that the query performance might suffer because I will need to jam too much and redundant logics into one query.

Instead, I want to accomplish it entirely in the SSRS report.

Before I create the hyperlink on the summary line, I created a new column “Running Values” to just test my idea of capturing those discrete dates per employee.

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I named this column “Running Values”, because I know that the RunningValue() VB function is what I need to use. A while ago I blogged about this wonderful aggregate function.

SSRS #72 – Use RunningValue() Function to Concatenate Row Values

As a matter of fact, all the aggregate functions in the following screenshot allow you to do aggregation within a group in SSRS.

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RunningValue() function needs an expression, an aggregate function and a group name

To use the RunningValue() function, I’ll need three parameters.

  • An expression, which normally is a field name, such as Yearly Income.
  • An aggregate function, such as MAX, SUM.
  • An group name, which is called GROUP_EMP in my report.

It is quite obvious that using the RunningValue() function out-of-box will not work for me, because I am not doing any direct aggregation on dates per employee.

It’s time to go back to my old blog, SSRS #72 – Use RunningValue() Function to Concatenate Row Values.

A VB script that simply concatenate the dates per GROUP_EMP

What I need is a VB script that allows me to simply concatenate the dates per GROUP_EMP. Every time the script is called, it keeps the prior dates, and adds the new date to the concatenated string.

This function will do exactly that. In Report –> Report Properties window, write the following code, making sure that the two strings aStr and tempStr are defined outside the Public Function/End Function block. This will make sure that both aStr and tempStr are saved per GROUP_EMP.

 

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Here is the code in text.

Dim aStr as String = “”
Dim tempStr as String = “”

Public Function ConcatenateString_Dates (ByVal inEmployee_ID As String, ByVal inDays As String) As String

If inEmployee_ID = aStr Then
tempStr = tempStr + “,” + inDays
Else
aStr = inEmployee_ID
tempStr = inDays
End If

Return tempStr

End Function

 

Calling the RunningValue() function from the test column

Now it’s time to use the RunningValue() function.

In this test column RunningValues, I need to call the RunningValue() function.

 

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Here is the actual code I used.

=RunningValue(Code.ConcatenateString_Dates(Fields!EMPLOYEE_ID.Value, Fields!CAL_DAY_LOCAL.Value), Max, “Group_Banker”)

The trick is in the first parameter, the expression.

Code.ConcatenateString_Dates(Fields!EMPLOYEE_ID.Value, Fields!CAL_DAY_LOCAL.Value)

This expression is not a simple field, it is the VB script I just created to concatenate the dates per employee.

The aggregation function I used is MAX. This allows me to get the last concatenated string, which is all the dates within one GROUP_EMP.

URL encoding allows more robust drill-through design

Now I am ready to just pass the following as a dates parameter to my next report.

RunningValue(Code.ConcatenateString_Dates(Fields!EMPLOYEE_ID.Value, Fields!CAL_DAY_LOCAL.Value), Max, “Group_Banker”)

Calling another SSRS report, or creating a drill-through report is normally pretty straightforward. SSRS has an out-of-box feature called Action for textboxes that can do that perfectly. But to make your reports more robust, and lasting long after the developer has moved on, there is something called URL encoding that VB scripts are good at. That can be another blog topic.

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