组合两个（表或列表）以创建 Power BI 中唯一组合的 output

Question

Trying to combine two queries in Power BI to have an output of unique combinations.

for instance one list(or column): A, B, C

and another list(or column): 1, 2, 3, 4, 5, 6, 7

Output should be: A1, A2, A3, A4, A5, A6, A7, B1, B2, B3, B4, B5, B6, B7, C1, C2, C3, C4, C5, C6, C7

Is there a way to accomplish this? (Yes my rows are not equal in count) Just don't know the best or right approach for this (tried using combine with a helper column and hit a dead end as duplicates get created, unless I did that wrong)

Answer 1

This is essentially a Cartesian product (aka cross product) of two lists.

If you just have two text lists, you can do a one-liner like this:

List.Combine(List.Transform(List1, (L1) => List.Transform(List2, (L2) => L1 & L2)))

This says for each item X in the first list, create a list that is the second list with X prepended to each element. This gives a list of lists that is flattened out to a single list using the combine function.

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It's not uncommon to want to do this with table though too. In this case, the analogous idea is to define a new column on one table where each row is the entire list/column of the other and then expand that new column.

Assuming we want the cross product of Table1[Column1] and Table2[Column2] :

let
    Table1 = <Table1 Source>,
    AddCustom = Table.AddColumn(Table1 , "Custom", each Table2),
    Expand = Table.ExpandTableColumn(AddCustom, "Custom", {"Column2"}, {"Column2"}),
    Concatenate = Table.AddColumn(Expand, "Concatenate", each [Column1] & [Column2])
in
    Concatenate

Edit: You can do the concatenation before the expand too:

let
    Table1 = <Table1 Source>,
    AddCustom = Table.AddColumn(Table1 , "Custom",
                    (T1) => List.Transform(Table2[Column2], each T1[Column1] & _)),
    Expanded = Table.ExpandListColumn(AddCustom, "Custom")
in
    Expanded

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References with more detail:

Cartesian Product Joins

Cartesian Join of two queries...