MySQL中删除多余的重复记录

Posted 2020-08-29 Milton

检查重复记录

-- 检查重复code1
select count(identity) num, identity from event_log 
where code=‘code1‘ 
group by identity having count(identity) > 1
order by num desc

删除重复记录

DELETE FROM event_log WHERE `code`=‘code1‘ AND identity IN (
    SELECT identity from (
        SELECT identity FROM event_log WHERE code=‘code1‘ GROUP BY identity HAVING count(identity) > 1
    ) a
) AND id NOT IN (
    SELECT keepId FROM (
        SELECT min(id) keepId FROM event_log WHERE code=‘code1‘ GROUP BY identity HAVING count(identity) > 1
    ) b
)

其中 a 和 b 两个中间表的作用是, 避免执行时出现  You can‘t specify target table ‘xxxxx‘ for update in FROM clause 错误