NULLs and Other Pitfalls
A NULL value represents the absence of data, in other words, data that is missing or unknown. When coding queries, stored procedures, or any other T-SQL, it is important to keep in mind the nullability of data because it will affect many aspects of your logic. For example, the result of any operator (for example, +, -, AND, and OR) when either operand is NULL is NULL.
Many functions will also return NULL when an input is NULL. This chapter discusses how to use SQL Server’s built-in functions and other common logic to overcome some of ...