Bruce Momjian: The NOT IN NULL Trap (Part 5/11)

As a corollary to three-valued logic expressed in the previous blog, NOT IN comparisons are a regular source of surprise. Consider this comparison of one against various values:

SELECT 1 
 2 AND 1 
 3;
 ?column?
----------
 t
 
SELECT 1 
 2 AND 1 
 3 AND 1 
 NULL;
 ?column?
----------
 (null)

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