Oracle将一个表中的字段更新到另一表中

• Demo

UPDATE cir_fin
SET cir_fin.currentrdtype = (
    SELECT
        reader.rdtype
    FROM
        reader
    WHERE
        reader.rdid = cir_fin.rdid
    AND cir_fin.currentrdtype IS NULL
)
WHERE
    EXISTS (
        SELECT
            reader.rdtype
        FROM
            reader
        WHERE
            reader.rdid = cir_fin.rdid
        AND cir_fin.currentrdtype IS NULL
    )