Conditional sum in Tableau

Question

I am just starting out with Tableau and have a question.

I have a star schema data warehouse with a fact table containing an "Amount", joined to a dimension containing "Event types"

Two event Types are "Settled" and "Cancelled"

I want to create a calculated measure in Tableau "Net Amount" which is the difference between the sum of Settled and Cancelled.

How do I do that?

I tried

SUM(IIF(Event_type_name = "Settled",Amount,0))-SUM(IIF(Event_type_name = "Cancelled",Amount,0))

but it returns a blank string 

Answer 1

Use ZN Function for converting null to zero

ZN function is a last logical function, and it has variations ISNULL and IFNULL

If a function is null it will return zero value

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