Goal: Add a "Sales" column to the Product table on the fly.
ADDCOLUMNS: Returns a table with original columns + new calculated ones.
Ready...
💻 DAX Formula
-- Create a temporary table with extra info
EVALUATE Enhanced_Table =
ADDCOLUMNS(
Products, -- 1. Source Table
"Total Sales", -- 2. New Column Name
SUMX( RELATEDTABLE(Sales), Sales[Amt] ) -- 3. Expression
)