What All Microsoft BI Developers What All Microsoft BI Developers Need to Know About MDXNeed to Know About MDX

Speaker: Nathan Peterson

Solid Quality Mentors

Silicon Valley SQL Server User Group

January 19, 2009

Mark Ginnebaugh, User Group Leader, mark@designmind.com

Nathan PetersonNathan Peterson

� Solid Quality Mentors

�Currently working on an Analysis Services project for the US Army

� Lead developer of a local cube generating utility called CubeSlice

What do all developers need to know about What do all developers need to know about MDX? MDX?

� You should be able to:

� Create and debug Calculated Members.

� Create and debug Named Sets.

What you need to know to accomplish this:� What you need to know to accomplish this:

� Understand MDX Concepts.

� Learn MDX Syntax.

� Learn some MDX functions.

� Learn some practical applications of MDX.

What Is MDX?What Is MDX?

� Multi-Dimensional eXpressions

� SQL is used for relational queries, while MDX is used for multidimensional queries.

� Calculated members allow you to incorporate � Calculated members allow you to incorporate multidimensional logic into your cube.

� Named sets allow you to pre-define dynamic groups of members to be displayed on columns or rows.

Sample calculated memberSample calculated member

with member measures.[Last Year Sales Amount]as(measures.[Sales Amount], measures.[Sales Amount], ParallelPeriod

([Date].[Calendar].[Calendar Year],1,[Date].[Calendar].CurrentMember)

)

Sample named setSample named set

with set [Top 5 Products]astopcounttopcount

([Product].[Product].Members,5,Measures.[Internet Sales Amount])

Comparing MDX to SQLComparing MDX to SQL

� From

� SQL selects from a table.

�MDX selects from a cube.

� Dimensionality � Dimensionality

� SQL returns one or more columns and 0 or more rows.

�MDX can return data for 0, 1, 2, 3 or more axes.

� Where

� SQL has a filter.

�MDX has a slicer.

MDX query with two axes and two slicersMDX query with two axes and two slicers

select Measures.AllMembers on columns,[Date].[Calendar].&[2003].Children on rowsfrom [Adventure Works]from [Adventure Works]where ([Customer].[Customer Geography].[France],[Product].[Product Categories].[Bikes])

Dimensions and MeasuresDimensions and Measures

Same query, using axis numbers instead of axis Same query, using axis numbers instead of axis namesnames

select Measures.AllMembers on 0,[Date].[Calendar].&[2003].Children on 1from [Adventure Works]from [Adventure Works]where ([Customer].[Customer Geography].[France],[Product].[Product Categories].[Bikes])

Using MDX requires multidimensional thinkingUsing MDX requires multidimensional thinking

� In a cube

� Dimensions have hierarchies

� Hierarchies have levels

� Levels have members� Levels have members

� In a cellset

� Each axis contains a set

� Each set consists of a group of members or a group of tuples

� Tuples have members from different hierarchies

Multidimensional thinking Multidimensional thinking –– Where are you?Where are you?

� Every member is in a level.

� Every level is in a hierarchy.

� Every hierarchy is a part of a dimension.

� For every cell of the cellset, there’s (almost) always a Current Member for each hierarchy.

� The Current Member may be set from the column, the row, the slicer, or the default member.

Create a set by listing membersCreate a set by listing members

� The simplest set is a list of members.

� The boundaries of the set are indicated with curly braces {}.

selectselect{[Product].[Category].[All Products],[Product].[Category].[Accessories],[Product].[Category].[Bikes],[Product].[Category].[Clothing],[Product].[Category].[Components]} on 0from [Adventure Works]

Create a set with a functionCreate a set with a function

� There are many MDX functions that create sets.

� This query uses the .Members function to return all the members from a hierarchy – and gives the same result as the previous query.result as the previous query.

� You don’t have to use {} when you create a set with a function.

select [Product].[Category].Members on 0from [Adventure Works]

TuplesTuples

� Each cell in a cellset shows data for one particular member from each hierarchy.

� A tuple is a way of specifying which member should be used from each of the hierarchies.be used from each of the hierarchies.

� Tuples are written like points in a geometric grid:

� (6,3) identifies point 6 on the x-axis and point 3 on the y-axis.

� ([2009],[US],[Bikes],[Internet Sales Amount]) identifies Internet Sales for Bikes in the US in 2009.

2 Dimensional 2 Dimensional TupleTuple

6

5

4

3

2 Dimensional Tuple

1 2 3 4 5 6 7 8

3

2

1

(6, 2)

Create a set by listing tuplesCreate a set by listing tuples

select{([Date].[Calendar Year].&[2002],[Product].[Category].[Accessories]),(

[Date].[Calendar Year].&[2002],[Date].[Calendar Year].&[2002],[Product].[Category].[Bikes]),(

[Date].[Calendar Year].&[2003],[Product].[Category].[Accessories]),(

[Date].[Calendar Year].&[2003],[Product].[Category].[Bikes])

}

on 0from [Adventure Works]

Listing Listing TuplesTuples

([2006], [Mountain Bikes])

2 Dimensional Tuple

[Accessories]

[Clothing]

[Touring Bikes]

[Road Bikes]

1 2 3 4 5 6 7 8

([2006], [Mountain Bikes])

2 2 2 2 2 2 2 20 0 0 0 0 0 0 00 0 0 0 0 0 0 0

[Road Bikes]

[Mountain Bikes]

[All Products]

Create a set of tuples by multiplying two sets of Create a set of tuples by multiplying two sets of membersmembers

select {

[Date].[Calendar Year].&[2002],[Date].[Calendar Year].&[2003]

}}*{

[Product].[Category].[Accessories],[Product].[Category].[Bikes]

}on 0from [Adventure Works]

3 Dimensional 3 Dimensional TupleTuple

[Accessories]

[Clothing]

[Touring Bikes]

[Road Bikes]([2006], [Mountain Bikes], [Red])

3 Dimensional Tuple Difficult to Show in 3 Axes –Where to place the point?

1 2 3 4 5 6 7 8

[Road Bikes]

[Mountain Bikes]

[All Products]

([2006], [Mountain Bikes], [Red])

2 2 2 2 2 2 2 20 0 0 0 0 0 0 00 0 0 0 0 0 0 0

[Red][Blue]

[Pink]

3 Dimensional 3 Dimensional TupleTupleCombining 2 Hierarchies on 1 AxisCombining 2 Hierarchies on 1 Axis

([Blue], [Road Bikes])

([Red], [Road Bikes])

([Blue], [Mountain Bikes])

([Red], [Mountain Bikes])

3 Dimensional Tuple

1 2 3 4 5 6 7 8

([Red], [Mountain Bikes])

([Blue], [All Products])

([Red], [All Products])([2006], [Mountain Bikes], [Red])

2 2 2 2 2 2 2 20 0 0 0 0 0 0 00 0 0 0 0 0 0 0

The Where clauseThe Where clause

� The Where clause is an optional part of an MDX query.

� The Where clause is a slicer, not a filter.

� You can’t use the Where clause for limiting the value to � You can’t use the Where clause for limiting the value to a threshold (Sales over $10,000).

� Use the Filter function for filtering.

� The Where clause often looks like a tuple and actually is a tuple – but it doesn’t have to be.

Where clause using a tuple Where clause using a tuple –– one member from one member from each referenced hierarchyeach referenced hierarchy

select Measures.[Internet Sales Amount] on 0from [Adventure Works]from [Adventure Works]where ([Customer].[Customer Geography].[France],[Product].[Product Categories].[Bikes])

Where clause with slicing on multiple members Where clause with slicing on multiple members from one hierarchyfrom one hierarchy

select Measures.[Internet Sales Amount] on 0from [Adventure Works]where where ([Customer].[Customer Geography].[France],

{[Product].[Product Categories].[Bikes],[Product].[Product Categories].[Clothing]}

)

The With clauseThe With clause

� The With clause is used for creating both calculated members and named sets.

� These calculated members and named sets are only valid for the life of the query.valid for the life of the query.

� You can also create calculated members and named sets that are persistent:

� Lasting for the life of a session.

� Created permanently in the cube.

Creating calculated member in the With clauseCreating calculated member in the With clause

with member Measures.[Average Internet Sales]as[Measures].[Internet Sales Amount][Measures].[Internet Sales Amount]/[Measures].[Internet Order Count],format_string = "currency"select {Measures.[Average Internet Sales]} on 0from [Adventure Works]

Members, Sets, Members, Sets, TuplesTuples

Set of

(Partial)

([Blue], [Road Bikes])

([Red], [Road Bikes])

([Blue], [Mountain Bikes])

([Red], [Mountain Bikes])

Members, Sets, Tuples

Member

Set of Members

(Partial)

Tuples

1 2 3 4 5 6 7 8

([Red], [Mountain Bikes])

([Blue], [All Products])

([Red], [All Products])([2006], [Mountain Bikes], [Red])

(Partial) Tuple

2 2 2 2 2 2 2 20 0 0 0 0 0 0 00 0 0 0 0 0 0 0

Creating named set in the With clauseCreating named set in the With clause

with set [Products - High Selling on Internet]asfilter

(([Product].[Product].[Product].Members,[Measures].[Internet Sales Amount]

> 50000)

select {Measures.[Internet Sales Amount]} on 0,[Products - High Selling on Internet] on 1from [Adventure Works]

Full Full TupleTuple

([Blue], [Road Bikes])

([Red], [Road Bikes])

([Blue], [Mountain Bikes])

([2006], [Mountain Bikes], [Red], [All

Promotions], [All Gender],

[Measures].[Reseller Sales Amount],

etc…)

1 2 3 4 5 6 7 8

([Red], [Mountain Bikes])

([Blue], [All Products])

([Red], [All Products])

etc…)

2 2 2 2 2 2 2 20 0 0 0 0 0 0 00 0 0 0 0 0 0 0

MDX PunctuationMDX Punctuation

� Use {} for sets.

� Use () for tuples.

� Use [] for names of cubes, dimensions, hierarchies, � Use [] for names of cubes, dimensions, hierarchies, levels, and members.

� Use commas all over the place (except not between multiple calculated members or named sets defined in the same query).

Where to write your MDXWhere to write your MDX

� In a client application like PerformancePoint, which allows you to write code for calculated measures and sets.

In a query editor like the SQL Server Management � In a query editor like the SQL Server Management Studio.

� In the MDX Script of a cube.

TIP: It’s often easier to write the code in a query editor first and then put it into the MDX Script.

Writing MDX for a KPIWriting MDX for a KPI

� You can write MDX to create the values for a KPI, whether you’re working with Analysis Services KPIs or PerformancePoint Services KPIs.

For both tools, it’s easier to create calculated � For both tools, it’s easier to create calculated members in the MDX script for the values first.

� TIP: When building KPIs in the BIDS, use a template for assigning the Status and the Trend.

Functions Functions –– Navigating within a levelNavigating within a level

� PrevMember

� NextMember

� Lag()� Lag()

� Lead()

Examples of navigating in a levelExamples of navigating in a level

� Navigation functions are often used with Dates.

� Note: PrevMember, Lag(1), and Lead(-1) all return the same member.

[1997].PrevMember[1997].PrevMember[1996]

[March 2010].NextMember [April 2010][10 April 2009].Lag(2) [8 April 2009][December 2009].Lead(12) [December 2010]

Functions Functions –– All in the FamilyAll in the Family

� Parent

� Children, FirstChild, LastChild

� DescendantsDescendants

� Ancestor, Ascendants

� Siblings, FirstSibling, LastSibling

� Cousin

Examples of family functionsExamples of family functions

� Some of the family functions return individual members, while other return sets.

� If a function returns an individual member, you can use another function with it.

[Mar 1997].Parent [1997][Q1 2009].Children [Jan 09]:[Mar 09][2009].FirstChild [Q1 2009]Descendants([2009], 2) [Jan 09]:[Dec 09]Descendants([2009],[Date])[1Jan09]:[31Dec09]Ancestor([Mar 2008], 3) [2008]FirstSibling([Mar 2007]) [Jan 2007]

Functions Functions –– Multiplying, adding, subtracting, Multiplying, adding, subtracting, intersecting setsintersecting sets

� Set multiplication, addition, and subtractions can be indicated with mathematical symbols or with functions.

Multiplication * Crossjoin

Addition + Union

Subtraction - Except

Intersection Intersect

Example of set multiplicationExample of set multiplication

� These two sets are equivalent.

[Date].[Fiscal].[Month].members* [Product].[Product].members[Product].[Product].members

Crossjoin([Date].[Fiscal].[Month].members,[Product].[Product].members)

Practical Applications of MDXPractical Applications of MDX

� Comparing with a previous time period.

� Comparing with the same time period in the previous year.

� Year-To-Date.

� Rolling Average.

� Percent contribution.

Comparing with a previous time periodComparing with a previous time period

with member Measures.[Last Month Sales]as(Measures.[Internet Sales Amount],[Date].[Calendar].PrevMember[Date].[Calendar].PrevMember)select{Measures.[Internet Sales Amount],Measures.[Last Month Sales]} on 0,[Date].[Calendar].[Month].members on 1from [Adventure Works]

Comparing with the same period in the previous Comparing with the same period in the previous yearyear

with member measures.[Last Year Sales Amount]as(measures.[Sales Amount], measures.[Sales Amount], ParallelPeriod

([Date].[Calendar].[Calendar Year],1,[Date].[Calendar].CurrentMember)

)

YearYear--ToTo--Date Date

with member measures.[YTD Sales]assum(ytd([Date].[Calendar].CurrentMember),ytd([Date].[Calendar].CurrentMember),Measures.[Internet Sales Amount])

select{Measures.[Internet Sales Amount],Measures.[YTD Sales]} on 0,[Date].[Calendar].[Month].members on 1from [Adventure Works]

Rolling AverageRolling Average

With member measures.[Previous 6 Month Rolling AVG]assum([Date].[Calendar].lag(6):[Date].[Calendar].lag(6):[Date].[Calendar].lag(1),

Measures.[Internet Sales Amount]) / 6

select{Measures.[Internet Sales Amount],Measures.[Previous 6 Month Rolling AVG]} on 0,[Date].[Calendar].[Month].members on 1from [Adventure Works]

Percent ContributionPercent Contribution

With member Measures.[Percent of Parent Sales]asMeasures.[Internet Sales Amount]/(Measures.[Internet Sales Amount],Measures.[Internet Sales Amount],[Product].[Product Categories].Parent)

select{Measures.[Internet Sales Amount],Measures.[Percent of Parent Sales]} on 0,[Product].[Product Categories]. members on 1from [Adventure Works]

Additional topics Additional topics –– if there’s timeif there’s time

� Dealing with exceptions

� String manipulation

� GenerateGenerate

� Recursion

Dealing with exceptionsDealing with exceptions

� A calculation needs to be valid everywherewith member [Measures].[% Change # of Customers]ascasewhen [Date].[Fiscal].CurrentMember.Level.Ordinal = 0 then "NA” when [Date].[Fiscal].CurrentMember.Level.Ordinal = 5 then Null when [Date].[Fiscal].CurrentMember.Level.Ordinal = 5 then Null when isempty

( ([Date].[Fiscal].CurrentMember.PrevMember, [Measures].[Customer Count])) then null

else( ([Date].[Fiscal].CurrentMember, [Measures].[Customer Count])-([Date].[Fiscal].PrevMember, [Measures].[Customer Count])) /([Date].[Fiscal].PrevMember,[Measures].[Customer Count])end

Functions Functions -- String manipulationString manipulation

� Turning the current date into a member reference

Strtomember((

"[Date].[Fiscal].[Date].&["+ cstr(year(now()) - 6)+ right("0" + cstr(month(now())), 2)+ right("0" + cstr(day(now())), 2)+ "]"

)

The Generate functionThe Generate function

� What are the five top products most purchased by people living in my top five cities?

generate(topcounttopcount([Customer].[Customer Geography].[City].members,5,[Measures].[Internet Sales Amount] ),

crossjoin([Customer].[Customer Geography].CurrentMember,topcount([Product].[Product].[Product].members,5,[Measures].[Internet Sales Amount]

) ) )

RecursionRecursion

� Finding the most recent purchase

with member measures.[Most Recent Purchase]member measures.[Most Recent Purchase]asiif

([Measures].[Internet Sales Amount] > 0,[Measures].[Internet Sales Amount],[Date].[Calendar].PrevMember)

Thank youThank you

� npeterson@solidq.com

� http://www.databasejournal.com/article.php/1459531/

� http://msdn.microsoft.com/en-us/library/ms145970.aspx

� http://www.sqlserveranalysisservices.com

� http://www.ssas-info.com/analysis-services-faq/27-mdx

� http://www.mosha.com/msolap/mdx.htm

� http://cwebbbi.spaces.live.com

To learn more or inquire about speaking opportunities, please contact:

Mark Ginnebaugh, User Group Leader

mark@designmind.com