ISNULL() has its own oddities:
DECLARE @var1 char(1)
SET @var1 = NULL
SELECT ISNULL(@var1, 'N/A') -- Result = 'N'
SQL DBA,SQL Server MVP(07, 08, 09) "It's a dog-eat-dog world, and I'm wearing Milk-Bone underwear." "Norm", on "Cheers". Also from "Cheers", from "Carla": "You need to know 3 things about Tortelli men: Tortelli men draw women like flies; Tortelli men treat women like flies; Tortelli men's brains are in their flies".