TOPN – first N rows from table (DAX – Power Pivot, Power BI)
This is about the TOPN DAX function, enabling us to see first (last) n rows from table.
Let´s start with this table, containing total revenue for items.
To see first three items with highest revenue, the syntax is:
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Items with highest revenue = topn(3;'Table';'Table'[Total revenue];DESC)

But what if we started with table containing not summarized values, like this?
Then we have to add the summarizing function and get three items from table provided by it:
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Items with highest revenue (2) = topn(3;GROUPBY('original data';'original data'[Goods];"Total revenue";SUMX(currentgroup();'original data'[Revenue]));[Total revenue];desc)