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常用的有两种方法:
1、单语句法:
1)delete b from sys_test b ,(select *,max(uuid) from sys_test group by `name` having count(`name`) > 1) as d where b.uuid>d.uuid and b.name = d.name
delete b from sys_test b这一句是设置别名,delete语句一般直接接from,当需要设置from表别名是,需要把别名放在from之前,表示删除时是对该别名中内容进行删除。
from中不同的表用,分割,可以有子查询出来的表,后面再接where即可。
2)delete form user where id not in (select Id from (select Max(ID) as Id,姓名,身份证号 from User group by 姓名,身份证号) as t );
该方法效率略低
2、临时表法
1)、找出所有重复的数据,并把重复数据复制一条到临时表
select * into #temp1 from user group by `name` having count(`name`) > 1
2)、删除原表中的所有重复的数据
delete from user where name in (select `name` from user group by `name` having count(`name`) > 1);
3)、将临时表中的数据在插入回user表
insert into user select * from #temp1;
4)、删除临时表
drop #temp1;
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原文地址:http://www.cnblogs.com/guangshan/p/4478859.html