Solved: Re: joinAlgorithm and keyEqualityComparers - Page 2

Greg_Deckler · ‎01-06-2017

In looking at the documentation for Table.Join and Table.NestedJoin, there is a brief mention of optional parameters of joinAlgorithm and keyEqualityComparers. However, I cannot find any information on how to use these. Does anyone have any examples of these?

I particularly want to know if these can be used to support unequal matching conditions, for example, only join if > or < versus =.

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ImkeF · ‎01-06-2017

Now I feel really honoured - thank you guys 🙂

Honestly: I haven't recognized these 2 parameters before. And while the MS-documentation holds some things about the joinAlgorithms in here: https://msdn.microsoft.com/en-us/library/mt296614.aspx, there's zero about keyEqualityComparers.

But with regards to the desired relative comparison here (< or >), I dare to say that they probably wouldn't help, as M distinguishes between equality and relational comparisons.

So in order to not let you down here, please have a look at the following query, which performs a relative lookup (and will hopefully appeal to you DAX-masters 🙂 😞

let
    Table1 = #table({"Key1"},{{10},{20},{30},{40}}),
    Table2 = #table({"Key2"},{{9},{19},{29},{39}}),
    RelativeMerge = Table.AddColumn(Table1, "RelativeJoin", 
            (Earlier) => Table.SelectRows(Table2, 
                         each [Key2]<Earlier[Key1])),
    #"Expanded RelativeJoin" = Table.ExpandTableColumn(RelativeMerge, "RelativeJoin", {"Key2"}, {"Key2"})
in
    #"Expanded RelativeJoin"

(This is nested row-context: Yes, we have evaluation context in M as well & fortunately it doesn't behave like a moving target 🙂 )

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ImkeF · ‎05-29-2017

If you run into performance issues with these techniques, it's worth checking out if you can partition your tables: http://www.thebiccountant.com/2017/05/29/performance-tip-partition-tables-crossjoins-possible-powerq...

Imke Feldmann (The BIccountant)

If you liked my solution, please give it a thumbs up. And if I did answer your question, please mark this post as a solution. Thanks!

How to integrate M-code into your solution -- How to get your questions answered quickly -- How to provide sample data -- Check out more PBI- learning resources here -- Performance Tipps for M-queries

ImkeF · ‎01-07-2017

Hi @MarcelBeug,

have you come across this already? Any idea how to use these parameters?

Imke Feldmann (The BIccountant)

If you liked my solution, please give it a thumbs up. And if I did answer your question, please mark this post as a solution. Thanks!

How to integrate M-code into your solution -- How to get your questions answered quickly -- How to provide sample data -- Check out more PBI- learning resources here -- Performance Tipps for M-queries

MarcelBeug · ‎01-07-2017

Hi @ImkeF Now I'm honoured as well.

As a matter of fact: yes, I came across this parameter as well.
From the function syntax * I learned that it should be supplied as a list, so I just tried with a silly list to see what would happen:
= Table.Join(KlantTabel, "Klantnr", OrderTabel, "Klant", null, null, {Comparer.OrdinalIgnoreCase})

As expected, I got an error message:
Expression.Error: Local evaluation of Table.Join or Table.NestedJoin with key equality comparers is not suported.

So my conclusion is that this functionality would only be usable with query folding.
Otherwise I'm not able to verify this, so I can only provide this information and nothing really conclusive.

* I created myself an interesting dashboard that generates function information, including syntax.

Specializing in Power Query Formula Language (M)

ImkeF · ‎01-07-2017

Hi @MarcelBeug,

I'm really impressed by the pace of your learning. Meanwhile I'm learning from you 🙂

(Yes, I'm also running this kind of formula-overview, but in Excel in order to do full-text-searches when looking for functions that perform specific tasks :-))

Imke Feldmann (The BIccountant)

If you liked my solution, please give it a thumbs up. And if I did answer your question, please mark this post as a solution. Thanks!

How to integrate M-code into your solution -- How to get your questions answered quickly -- How to provide sample data -- Check out more PBI- learning resources here -- Performance Tipps for M-queries

MarcelBeug · ‎01-07-2017

In my Excel version (2016 from O365 subscription), the keyEqualityComparers are not included in Table.Join and Table.NestedJoin, so my research for this parameter was in Power BI Desktop.

Specializing in Power Query Formula Language (M)

joinAlgorithm and keyEqualityComparers

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