SELECT array_to_json(array_agg(outer))
FROM
(
SELECT
    eCPRefAuth_Action_Code_Lookup_Category2
(
SELECT array_to_json(array_agg(Result))
FROM
(
SELECT
    eCPRefAuth_Action_Code_Lookup_Category
    ,json_agg(
        row_to_json(
                        (
                            SELECT t FROM
                            (
                                SELECT eCPRefAuth_Action_Code_Lookup_Code, eCPRefAuth_Action_Code_Lookup_Desc
                                ORDER BY eCPRefAuth_Action_Code_Lookup_Seq_level2
                            )  AS t(eCPRefAuth_Action_Code_Lookup_Code, eCPRefAuth_Action_Code_Lookup_Desc)
                        )
                    )
            ) AS available_codes
FROM   tbl_eCPRefAuth_Action_Code_Lookup

GROUP  BY eCPRefAuth_Action_Code_Lookup_Category, eCPRefAuth_Action_Code_Lookup_Seq_level1
ORDER BY eCPRefAuth_Action_Code_Lookup_Seq_level1
) AS Result
)
FROM   tbl_eCPRefAuth_Action_Code_Lookup
)as outer