how can I create a view in sqldeveloper

Question

I am trying to add this query in a view, while test it works fine and no syntax error but when click save, I get this error

ORA-00907: missing right parenthesis

This is the query:

SELECT
    importer_id,
    AVG(count),
    STDDEV(count),
    AVG(count) + STDDEV(count) * 2 AS baseline
FROM
    (SELECT
         COUNT(declaration_identifier)        AS count,
         EXTRACT(MONTH FROM declaration_date) AS month,
         importer_id
     FROM
         declaration
     GROUP BY
         importer_id,
         EXTRACT(MONTH FROM declaration_date)
    )
GROUP BY
    importer_id

Answer 1

I created a dummy table to get your view to compile.

create table declaration
( declaration_identifier integer,
  declaration_date date,
  importer_id integer
  );

I then wrapped your query with a CREATE VIEW...

CREATE VIEW SO_ERROR
AS SELECT
    imp_id as id,
    AVG(count) as count,
    STDDEV(count) as stddev,
    AVG(count) + STDDEV(count) * 2 as baseline
FROM
    (
        SELECT
            COUNT(declaration_identifier)         count,
            EXTRACT(MONTH FROM declaration_date)  month,
            importer_id imp_id
        FROM
            declaration
        GROUP BY
            importer_id,
            EXTRACT(MONTH FROM declaration_date) 
    )
GROUP BY
    imp_id;

Note that every column in the outer select has an ALIAS.