mysql 去除重复数据

Posted 2020-09-30 rocky-fang

1. 问题描述

   有时load或者insert操作导致 表数据有重复

2. 解决方案

   通过临时表、主键id、倒腾去重

  示例

2.1  create table student(

　　name varchar(30) not null default ‘‘,

       age smallint(3) not null default 0,

　　love varchar(50) not null default ‘‘

)

插入一些数据......(包含重复)

insert into student(name,age,love) values(‘zhangsan‘,15,‘basketball‘);

insert into student(name,age,love) values(‘zhangsan‘,15,‘basketball‘);

insert into student(name,age,love) values(‘zhangsan‘,15,‘basketball‘);

2.2  备份(全部数据或部分数据)

create table student_backup like student;

insert into student_backup select * from student where name=‘zhangsan‘;

2.3 创建临时表一
create table student_tmp like student;

insert into student_tmp select * from student where name=‘zhangsan‘;

alter table student_tmp add id int primary key auto_increment not null ;

2.4 创建临时表二

create table tmp2 (

id int auto_increment not null,

primary key(id)

);

insert into tmp2 select min(id) as id from student_tmp group by name,age,love;

2.5 创建临时表三

create table tmp3 like student_tmp;

insert into tmp3 select student_tmp.*  from student_tmp,tmp2 where student_tmp.id=tmp2.id;

alter table tmp3 drop column id;

2.6 删除重复数据

delete from student where name=‘zhangsan‘;

2.7 插入去重后数据

insert into student select * from tmp3;

Done!