mysql 删掉重复数据

--不知道为啥这个mysql外边还要包一层，不然就报错
DELETE
FROM
    course  
WHERE
     name IN (
select mm.name from (
        SELECT
            a.name  as name
        FROM
            course a
        GROUP BY
            a. NAME
        HAVING
            count(a.NAME) > 1)mm
    )
AND  id NOT IN (
select nn.id from (
    SELECT
        min(id) as id
    FROM
        course a
    GROUP BY
        a. NAME
    HAVING
        count(a.NAME) > 1)nn
);