id毎に持っている日付の最大値を取得

①group byに、maxで取りたい項目名は不要
②where句の[so.create_date = A.create_date]が肝

SELECT
    so.id,
    so.create_date
FROM
    so,
    (SELECT
        id,
        max(create_date) as create_date
    FROM
        so
    GROUP BY
        id
    ) as A
WHERE
    so.create_date = A.create_date AND
    so.id = A.id