Goal: Count how many unique customers bought something.
Watch how DISTINCTCOUNT remembers duplicates.
Ready...
💻 DAX Formula
-- Scenario 1: Count Every Transaction
MEASURE Total_Txns = COUNT( Sales[Customer] )
-- Counts Alice 3 times if she bought 3 times.
-- Scenario 2: Count Unique Customers
MEASURE Unique_Cust = DISTINCTCOUNT( Sales[Customer] )
-- Ignores duplicates. Alice is counted once.