DELETE consum_record FROM consum_record, ( SELECT min(id) id, user_id, monetary, consume_time FROM consum_record GROUP BY user_id, monetary, consume_time HAVING count(*) > 1 ) t2 WHERE consum_record.user_id = t2.user_id and consum_record.monetary = t2.monetary and consum_record.consume_time = t2.consume_time AND consum_record.id > t2.id;
上面这条sql语句，仔细看一下，揣摩出思路也不难，大概也分为3步来理解：
(SELECT min(id) id, user_id, monetary, consume_time FROM consum_record GROUP BY user_id, monetary, consume_time HAVING count(*) > 1 ) t2
查询出重复记录形成一个集合（临时表t2），集合里是每种重复记录的最小ID
consum_record.user_id = t2.user_id and consum_record.monetary = t2.monetary and consum_record.consume_time = t2.consume_timeANDconsum_record.id > t2.id;
关联 判断重复基准的字段
根据条件，删除原表中id大于t2中id的记录
看到这个语句的时候，心里想这也太厉害了。这么一个简单的sql语句，竟然可以解决这么复杂的问题，涨姿势了~不得不佩服思路啊！
又找到一条SQL实现去重保留一条记录，分享给大家：
delete from cqssc where id in (select id from (select id from cqssc where expect in (select expect from cqssc group by expect having count(expect)>1) and id not in(select min(id) from cqssc group by expect having count(expect)>1)) as tmpresult)
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