Found an interesting post about the SQL ISNULL function.  Apparently, it behaves differently if you’re using it to test strings.  For example:

DECLARE @a VARCHAR(100)
DECLARE @b VARCHAR(10)

SET @a=’This is much longer than 10 characters‘
SET @b=NULL

— This will display
—        This is mu
SELECT ISNULL(@b,@a)

— This will display
—        This is much longer than 10 characters
SELECT ISNULL(CONVERT(NVARCHAR(MAX), @b), @a)

Knowing this could keep you from pulling your hair out trying to investigate a bug when the truncated data gets down the pipeline.  Hope that helps someone out there.

Happy Coding!