order by in subselect not performed

following statement represents a simplified query; I simulate a 3-row table with a union statement.
order by in the inner subselect does not affect the order of the outer select
in mysql it does.
statement:
SELECT * FROM (SELECT * FROM (SELECT 'a' UNION SELECT 'b' UNION SELECT 'c' )t order BY a desc)t
result: a,b,c
in Mysql: c,b,a (correct)