DAX: CALCULATETABLE how restrict rows found to max 1 per User ID

[iplaygod]

Hi all

I have a sales table. Each row in the sales table has the field [User ID] indicating who made that purchase.
So there are multiple rows for each User ID. The number of sales rows per User ID depends on their purchase history.

I am trying to write a calculatetable that will give me only max 1 sales row per unique User ID found in the sales table.
I want the first row that matches the filter I am applying, for each unique User ID.

The problem with my current code is that it is retrieving several sales rows for some users (who happen to have several rows matching my filter)

The current filter context will filter the sales table by a date range etc.
I then add to that filter context.
What I have now is:

VAR filteredRowsTable = 
    CALCULATETABLE(sales;
        FILTER(sales;
            sales[flag one] = 1
            && sales[flag two] = 1
            && RELATED(products[Product Line]) = "Shoes"
        )
    )

How can I change the code to accomplish my goal?

Basically, the pseudo code is:
Apply the filter to the sales table
Now extract distinct User IDs from that filtered table
Now give me only the first found sales row, from the filtered rows in the sales table, for each of those distinct User IDs

Please give me some code example.
Thanks!

thanks

[Zubair_Muhammad]

@iplaygod

Try this

VAR filteredRowsTable =
    CALCULATETABLE (
        sales,
        FILTER (
            sales,
            sales[flag one] = 1
                && sales[flag two] = 1
                && RELATED ( products[Product Line] ) = "Shoes"
        )
    )
VAR RankRowsforeachID =
    ADDCOLUMNS (
        filteredRowsTable,
        "RANK", RANKX (
            FILTER ( filteredRowsTable, [User ID] = EARLIER ( [User ID] ) ),
            [Sales],
            ,
            DESC,
            DENSE
        )
    )
VAR TablewithMaxRows=
    FILTER ( RankRowsforeachID, [RANK] = 1 )

[Zubair_Muhammad · Accepted solution]

@iplaygod

Another way could be to use TOPN function

=
VAR TOPROWS =
    GENERATE (
        VALUES ( Sales[User ID] ),
        VAR mytable =
            CALCULATETABLE ( TOPN ( 1, Sales, [SalesColumn], DESC ) )
        RETURN
            SUMMARIZE ( mytable, [SalesColumn] )
    )
VAR filteredRowsTable =
    CALCULATETABLE (
        sales,
        TOPROWS,
        FILTER (
            sales,
            sales[flag one] = 1
                && sales[flag two] = 1
                && RELATED ( products[Product Line] ) = "Shoes"
        )
    )
RETURN
    filteredRowsTable

[iplaygod]

thanks for the suggestions!

i will try and get back