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MySql常用的sql语句

1. 查找出多字段出现重复数据次数

select 
	aid,count(*) as count -- 数据重复出现的次数
from pics 
group by aid, filename
having count(*) > 1;

2. 删除多字段出现重复数据只保留最后一条

delete a.* from pics as a
where a.id <> (
	select
		min(b.id)
	from (
		select * from pics
	) as b
	where a.`aid`= b.`aid` and a.filename = b.filename
);