NULL Tests Step by Step

A compact NULL-test book for readers who need exact finite IS NULL and IS NOT NULL behavior: base rows with missing and present values, TRUE/FALSE rows with no UNKNOWN, truth inversion, missing-value selection, present-value selection, TRUE-only source-order output, and guarded expected facts.

NULL Tests

Base Rows
IS NULL TRUE for NULL
IS NULL FALSE for Present
No UNKNOWN for IS NULL
IS NOT NULL Inversion
Select Missing Values
Select Present Values
Honest by Construction