>>>>> "Chris" == Chris Wilson <chris.wilson@xxxxxxxxxxxxxxxxx> writes: Chris> However, if we try to invert it by using the != operator, then Chris> we get unexpected results: Mr. De Morgan would like a word. https://en.wikipedia.org/wiki/De_Morgan%27s_laws In short, if you have a condition of the form (a OR b) and you want to negate it, then you find that: NOT (a OR b) is equivalent to (NOT a) AND (NOT b) Since x = ANY (array[1,2]) is equivalent to (x = 1) OR (x = 2), then the negation would be (x != 1) AND (x != 2), not OR. Which can be conveniently expressed as x != ALL (array[1,2]). So just as you interchange AND and OR when inverting the sense of a condition, you also interchange ALL and ANY for exactly the same reasons. Chris> expression NOT IN (subquery) https://wiki.postgresql.org/wiki/Don%27t_Do_This#Don.27t_use_NOT_IN Chris> And is it a bug that one can't use unnest in a NOT IN expression Chris> in the WHERE clause? No. -- Andrew (irc:RhodiumToad)
