You have a transaction list. You want to analyze "New Customers" by finding the very first purchase date for every Customer ID, regardless of the date range selected in the view.
You have a dataset where one Order ID has multiple rows (different products). You want to count the distinct number of orders, but aggregation types can get tricky. tableau fixed calculation
Use FIXED when you need a dimension’s value regardless of what’s in the view (e.g., customer lifetime metrics). You have a transaction list