What is the result of an attempt to add, subtract, multiply, or divide two number fields, one of which contains a null value?

QUESTION: What is the result of an attempt to add, subtract, multiply, or divide two number fields, one of which contains a null value?   [signinlocker] SOLUTION   The Inclusion of a null value results in each of these computations yielding a null value as...

Which comparison operators can be used when searching for null values? Which comparison operators cannot be used when searching for null values?

QUESTION: Which comparison operators can be used when searching for null values? Which comparison operators cannot be used when searching for null values? What is the result when these unacceptable comparison operators are used when searching for null values?  ...

What is the difference between a character field that contains a null value and a character field that contains a single blank space?

QUESTION: What is the difference between a character field that contains a null value and a character field that contains a single blank space?   [signinlocker] SOLUTION   A character field that contains a null value is zero characters long, while a...