when lead() returns null on a datetime field, the result is treated as the literal string '[NULL]'

/* when lead() returns null on a datetime field, the result is treated as the literal string '[NULL]' */

	create temporary table d1(d datetime);

	insert into d1 values ('2018-01-01 00:00:00'),('2018-02-01 00:00:00');

	/* null record is not returned */

	select *

	from 

		(

			select *, lead(d) over (order by d) as x from d1

		) a

	where x is null

	/* null record is returned when treated as a string */

	select *

	from 

		(

			select *, lead(d) over (order by d) as x from d1

		) a

	where x = '[NULL]'

	drop table d1