Pentaho Mondrian: The MDX Generate Function


Repost from http://diethardsteiner.github.io/cde/2015/04/23/MDX-Generate-Function.html

This is a brief overview of how you can use the MDX GENERATE() function. All the examples below work with the SteelWheelsSales Cube, which ships with the Pentaho BA Server. Try the examples listed below either with Pentaho Analyzer, the Saiku CE plugin, Pivot4J or Roland Bouman’s Pentaho Analysis Shell (Pash) (The last 3 ones are plugins, which you can download via the Pentaho Marketplace).

The GENERATE() function has two different applications:

  • If the second parameter is a set, it will return the members that exist in both sets ( a UNION() of the sets). You can think of it as a kind of for-each function which checks if members in the first set exist in the second one. ALL can be used as a third parameter to keep any duplicates.
  • If the second parameter is a string expression then the members will be concatenated.

Examples:

Find the members that are in both sets:

SELECT
    [Measures].[Sales] ON 0
    , NON EMPTY GENERATE(
        {[Markets].[Country].[Australia], [Markets].[Country].[USA]}
        , [Markets].[Country].[Australia]
    ) ON 1
FROM [SteelWheelsSales]
Country Sales
Australia 630,623

In this case Australia survives, because it is a member of the first as well as the second set.

For each member of the first set retrieve the first child:

SELECT
    [Measures].[Sales] ON 0
    , NON EMPTY GENERATE(
        {[Markets].[Country].[Australia], [Markets].[Country].[USA]}
        , [Markets].currentMember.firstChild
    ) ON 1
FROM [SteelWheelsSales]
State Province Sales
NSW 305,567
CA 1,505,542

Next we’d like to know the top performing country within each territory:

SELECT
    [Measures].[Sales] ON 0
    , NON EMPTY GENERATE(
        [Markets].[Territory].Members
        , TOPCOUNT([Markets].CurrentMember.Children, 1, [Measures].[Sales])
    ) ON 1
FROM [SteelWheelsSales]
Country Sales
Australia 630623
Spain 1215687
Japan 188168
USA 3627983

Taking the previous example a bit further, we can get the top performing country and customer combination based on sales for each territory:

SELECT
    [Measures].[Sales] ON 0
    , NON EMPTY GENERATE(
        [Markets].[Territory].Members
        , TOPCOUNT([Markets].CurrentMember.Children * [Customers].[Customer].Members, 1, [Measures].[Sales])
    ) ON 1
FROM [SteelWheelsSales]
Country Customer Sales
Australia Australian Collectors, Co. 200,995
Spain Euro+ Shopping Channel 912,294
Singapore Dragon Souveniers, Ltd. 172,990
USA Mini Gifts Distributors Ltd. 654,858

There is also an option to retain duplicates in the results using the ALL flag as the third argument:

SELECT
    [Measures].[Sales] ON 0
    , NON EMPTY GENERATE(
        {[Markets].[Country].[Australia], [Markets].[Country].[Australia]}
        , [Markets].currentMember.firstChild
        , ALL
    ) ON 1
FROM [SteelWheelsSales]
State Province Sales
NSW 305,567
NSW 305,567

Now let’s have a look at a completely different way we can use the GENERATE() function:

Let’s show the territories with all their countries next to each other in one line. We can define a delimiter as the third parameter of the GENERATE() function:

WITH 
MEMBER [Measures].[Countries] AS
    GENERATE(
            [Markets].CurrentMember.Children
            , [Markets].CurrentMember.Name
            , "-"
        )
SELECT
    {[Measures].[Countries]} ON 0
    , NON EMPTY [Markets].[Territory].Members ON 1
FROM [SteelWheelsSales]
Territory Countries
#null Germany-Ireland-Israel-Netherlands-Poland-Portugal-Russia-Singapore-South Africa-Spain-Switzerland
APAC Australia-New Zealand-Singapore
EMEA Austria-Belgium-Denmark-Finland-France-Germany-Ireland-Italy-Norway-Spain-Sweden-Switzerland-UK
Japan Hong Kong-Japan-Philippines-Singapore
NA Canada-USA

As mentioned earlier, this is just a brief intro the extremely useful GENERATE() function. I hope that the example gave you some ideas on how to use this function.

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