Question: While converting some Access queries to T-SQL, I came across the Access function IIf. I read the documentation [here](https://support.microsoft.com/en-us/office/iif-function-32436ecf-c629-48a3-9900-647539c764e3) and understand it takes 3 parameters: the expression, the if true, and the if false. What I have yet to find is if the "false" param is required? And if a false is not provided, what is the behavior?

**UPDATE:**
When this question was asked, I did not ***know*** if the query worked with only 2 parameters (b/c I can not run the query in Access). I did, however, ***suspect it might work*** (with only 2 params) b/c a few queries I am converting (to T-SQL) have nested IIF's and the last IIF has only 2 params.

Answer: 
It's `IIf`, not `IFF`. All arguments are required in VBA and textbox expressions and both must be calculatable (no error result such as DivBy0) because both parts will be calculated - if either errors, the entire expression errors. The IIf() in Access query works differently - 'falsepart' calculates only if 'truepart' fails and if 'falsepart' is not provided, expression returns Null if 'truepart' fails.

Try some expressions and see what happens. One for testing: `IIf(1=2,"T")`.
Yes, it's required, it's actually like an if else statement.

i.e an action occurs if the condition is fulfilled, and another action occurs if condition is not fulfilled