Specifying NULL elements positioning in ordered columns

I don't know about other RDBMS but in MySQL ordering, it's possible to specify whether NULL column fields are placed in the beginning or at the end of the ordering, i.e.:

ORDER BY `values_column` IS NULL DESC
[values_column]
NULL
NULL
value1
value2
value3

or the other way around (ORDER BY `values_column` IS NULL ASC):
[values_column]
value1
value2
value3
NULL
NULL

I checked JDO 3 specification and found that JDOQL's ordering specification doesn't support specifying NULL values handling:
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26.7 Ordering Specification
This section describes the syntax of the setOrdering argument.
OrderingClause:
OrderingSpecs ,opt
OrderingSpecs:
OrderingSpec
OrderingSpecs , OrderingSpec
OrderingSpec:
Expression Ascending
Expression Descending
Ascending: one of
asc ascending
Descending: one of
desc descending
Please note, as a usability feature OrderingClause supports an optional trailing comma.
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Thank you for your time and efforts.