I have to write a query on a positively atrocious table (this is with MSSQL 2005). Basically, multiple "lists" are stored in a single gigantic table called "UserData". I'm building the SQL statement ...

RIGHT JOIN (or RIGHT OUTER JOIN): It’s the opposite of a LEFT JOIN. It keeps all rows from the right table and matches from the left. Less common than LEFT JOIN, but good to know it exists.