When would you ever want NULLS first when ordering a query descending or ascending?
In my opinion, the vast majority of the time the desired behavior whether sorting ascending or descending would be NULLS LAST. Instead, we should have to specify NULLS FIRST.
Actually, with default sort order (
ASCENDING) NULL values come last.
Logic dictates that the sort order be reversed with the
DESCENDING keyword, so NULLs come first in this case.
But the best part comes last: you can choose which way you want it:
Quoting the current manual, version 9.3 as of writing:
NULLS LASTis specified, null values sort after all non-null values; if
NULLS FIRSTis specified, null values sort before all non-null values. If neither is specified, the default behavior is
ASCis specified or implied, and
DESCis specified (thus, the default is to act as though nulls are larger than non-nulls). When
USINGis specified, the default nulls ordering depends on whether the operator is a less-than or greater-than operator.
Bold emphasis mine.