mysql操作重复数据

这两天为公司做的网络爬虫获取了一堆数据，存在不少重复的，需要在数据库中将重复的数据清除，学习了一下sql相关语句

1、先做备份咯：

CREATE TABLE salesback1 LIKE salesback;   
INSERT INTO salesback1 SELECT * FROM salesback;

2、查询一下有多少重复语句：

SELECT * FROM salesback1 WHERE  company IN (SELECT company FROM  salesback1  GROUP BY company HAVING  count(company) > 1

3、删除重复数据：

delete from sales where id in (select id from (select id from sales where company in (select company from sales group by company having count(company)>1)  
and id not in(select min(id) from sales group by company having count(company)>1) )a)

4、查询条数：

select count(*) from salesback1