NULL Values

Relational databases allow a special value NULL
Interpretation depends on the application: NULL could mean “Not applicable” or “unknown” or “hidden” or “not collected” or many other things

NULL or True = True

This expression will always be true

Is NULL equal to NULL?

no. bc NULL can be ✨anything✨

special syntax to test for NULL:

“x IS NULL” evaluates to True if x is NULL