MySQL数据库查询重复数据办法
只操作一个列数据找出重复
select * from table1 where v1 = X group by column1 having count(*)>1
通过对两个列进行操作找出重复,并只保留一条非重复信息
1.先通过max或者min函数对不相关列进行操作
select max(column1) from table1 group by column2;
2.嵌套把重复数据全部信息查出进行操作
select * from where column in(select max(column1) from table1 group by column2);
3.以上信息查出的都是单独的一条非重复数据(有用数据),现在删除其他无用数据
delete from column2 not in(select * from where column in(select max(column1) from table1 group by column2))