>>>>> "David" == David G Johnston <david.g.johns...@gmail.com> writes:

 >> 2. x IS NOT NULL  if and only if  NOT (x IS NULL)

 David> ​I would rather prohibit "IS NOT NULL" altogether.​ If one needs
 David> to test "NOT (x IS NULL)" they can write it that way.

Prohibiting IS NOT NULL is not on the cards; it's very widely used.

 >> Whole-row vars when constructed never contain the null value.

 David> ...but what does this mean in end-user terms?​

It means for example that this query:

  select y from x left join y on (x.id=y.id) where y is null;

would always return 0 rows.

Andrew (irc:RhodiumToad)

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