Tutorial by Topics: nulls

In SQL Server, NULL represents data that is missing, or unknown. This means that NULL is not really a value; it's better described as a placeholder for a value. This is also the reason why you can't compare NULL with any value, and not even with another NULL. SQL Server provides other methods...

The value null is the default value for an uninitialized value of a field whose type is a reference type. NullPointerException (or NPE) is the exception that is thrown when you attempt to perform an inappropriate operation on the null object reference. Such operations include: calling an inst...