Goal: Fetch data across tables.
RELATED: Pulls info from the "One" side (Lookup).
RELATEDTABLE: Counts rows on the "Many" side (Fact).
Ready...
💻 DAX Formula
-- Scenario 1: Fetch Price from Lookup Table
COLUMN Revenue = Sales[Qty] * RELATED( Product[Price] )
-- "Go look up the Price for this product"
-- Scenario 2: Count Sales for each Product
COLUMN Txn_Count = COUNTROWS( RELATEDTABLE( Sales ) )
-- "Go count how many times this product appears in Sales"
Relationship:
Sales[*]
────── related to ──────
Product[1]