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
)