Eric Blinn wants to know of those NULLs:
Many data professionals search for help writing T-SQL queries containing columns with NULL values in a Microsoft SQL Server table. Some of the most common NULL functions include IS NULL, IS NOT NULL, NOT NULL, NULL, what is NULL, NULL vs NOT NULL, etc. In this SQL tutorial, the goal is to help you better understand how to work with NULL values in a SQL database.
Even the best of us have accidentally used = NULL in a script when we meant IS NULL. Which is totally different from ISNULL(), of course. And NULLIF(), naturally.