I want to use a parameter query on a table. The query will specify three parameters. Two of which will always be present while the third may sometimes be null. When this third parameter is null I want it to return all records with a null value - except it doesn't work. I have tried the following code in the query to no avail.
IIF(ISNULL([Field 3:]), IS NULL, [Field 3:])
Using this code, if I enter a value for [Field 3:] it works fine. But when I leave [Field 3:] blank it doesn't match any records.