Can't select column I used in join-on statement

I'm modifying an SQL query so it will be database agnostic (and therefore also would work in SQL Server). This means I have replaced a join-using with a join-on. This worked, but when I placed that sub-query back into its parent I get an error.

I am getting an ORA-00904: study_event_id: invalid identifier error on the SELECT of a column I used in the ON statement of the JOIN.

The code below is stripped down a lot to the minimum where I get the error, so the subqueries and aliases need to be preserved as much as possible.

SELECT
    study_event_id
FROM
    (
        SELECT
            *
        FROM
            (
                SELECT
                    ea.*,
                    sbj.subject_id
                FROM
                    v_study_event ea,
                    v_subject     sbj
            ) lefttable
            LEFT OUTER JOIN (
                SELECT
                    *
                FROM
                    v_subject_current_event_status
            ) righttable ON righttable.study_event_id = lefttable.study_event_id
        
    ) tbl

I can select every other column, but the column I joined on can't be identified.

The column does appear when I SELECT *.

I have tried to specify it with all the above aliases: tbl, lefttable and righttable.

I just don't understand why that one column can't be selected.

In the full query this column is selected with a bunch more, and there are two columns in the join-on statement The other column also can't be selected, but I don't need that one further in the complete query.

The problem has been fixed. It seems the first select * gets confused. I had to write out all columns I needed from the joined views.

The columns study_event_id needed to be specified to lefttable.study_event_id.

This query worked:

SELECT
    study_event_id
FROM
    (
        SELECT
            lefttable.study_event_id study_event_id
        FROM
            (
                SELECT
                    ea.*,
                    sbj.subject_id
                FROM
                    v_study_event ea,
                    v_subject     sbj
            ) lefttable
            LEFT OUTER JOIN (
                SELECT
                    *
                FROM
                    v_subject_current_event_status
            ) righttable ON righttable.study_event_id = lefttable.study_event_id
        
    ) tbl