This can be confusing the first time you see it — it proves
that, in Oracle, Null is neither equal to nor not equal to Null.
SQL Server, by default, does not do it that way: in SQL Server
and sybase, Null is equal to Null. Neither Oracle's, sybase nor
SQL Server's SQL processing is wrong — they are just
different. Both databases are in fact ANSI compliant
databases but they still work differently....