Why does NULL = NULL evaluate to false in SQL server

Question

In SQL server if you have nullParam=NULL in a where clause, it always evaluates to false. This is counterintuitive and has caused me many errors. I do understa

Answer 1

The equality test, for example, in a case statement when clause, can be changed from

XYZ = NULL 

to

XYZ IS NULL

If I want to treat blanks and empty string as equal to NULL I often also use an equality test like:

(NULLIF(ltrim( XYZ ),'') IS NULL)