I just want to point something out that might help the original poster.
On Saturday, March 7, 2020, 7:00:21 AM EST,
sqlite-users-requ...@mailinglists.sqlite.org
<sqlite-users-requ...@mailinglists.sqlite.org> wrote: >
> 1. NULL is NULL = Yes, True,
> 2. NULL is FALSE = Nope, False.
> 3. NULL is TRUE = Nope, False.
> 4. NULL is NOT NULL = Nope, False,
> 5. NULL is NOT FALSE = Yep, True.
> 6. NULL is NOT TRUE = Yep, True.
> 7. TRUE is FALSE = Nope, False.
> 8. TRUE is NOT FALSE = Yep, True.
> 9. FALSE is NOT TRUE = Yep, True.
This explanation 100% correct and probably 80% confusing without the following,
especially because "is" is not capitalized:IS and IS NOT are logical operators
in SQL. NOT is not a unary operator when preceded by IS.
In most non-relational languages "NULL IS NOT TRUE" is parsed as:
value(NULL) operator(IS) (operator(NOT) value(TRUE)).
That is NOT how SQL works. In SQL, it is:
value(NULL) operator(IS NOT) value(TRUE).
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