Oracle SQL, is it possible to use a user-defined datatype property in a nested select?

Brackets :-)

select (obj).start_date from (select RETURN_OBJ() AS obj FROM DUAL)

sql oracle object return subquery

You must use a table alias when you like to access functions from OBJECT Types. Try this one:

SELECT t.obj.start_date FROM (SELECT RETURN_OBJ() AS obj FROM DUAL) t;

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