sql删除重复记录

--删除userName重复的数据只保留一条
DELETE
FROM
    users
WHERE
    userName IN (
SELECT
            t.userName
        FROM(
        SELECT
            userName
        FROM
            users
        GROUP BY
            userName
        HAVING
            count(userName) > 1) t
    )
AND Id NOT IN (
select t.id from (
    SELECT
        min(Id) as id
    FROM
        users
    GROUP BY
        userName
    HAVING
        count(userName) > 1) t
)