MySQL去重

一 mysql去重操作
1查看是否有重复数据（根据唯一字段name_s 查询表hc）
SELECT name_s,COUNT(*) FROM hc GROUP BY name_s  HAVING COUNT(*) > 1

2查询数据表中重复字段中的一个
select * from hc where name_s in (select  name_s from hc  group  by  name_s   having  count(name_s) > 1) 
and id in (select min(id) from  hc  group by name_s  having count(name_s)>1)

3mysql插入重复数据到另一个临时表hc2
insert into hc2 (select * from hc where name_s in (select  name_s from hc  group  by  name_s   having  count(name_s) > 1) and id not in (select min(id) from  hc  group by name_s  having count(name_s)>1))

4删除表一和表二中相同的数据
delete a.* from hc a, hc2 b where a.id = b.id ;

5如果想保持表1中id连续则创建表3将表一中除了id之外其他字段全部添加到表3
insert into hc3(name_s,mobile_s,phone_s,url_s,people_s) (select name_s,mobile_s,phone_s,url_s ,people_s  from hc)


二
1创建一个临时表，其中包含要删除的重复记录的 `Url` 值。
CREATE TABLE tmp_table AS SELECT Url FROM your_table_name GROUP BY Url HAVING COUNT(*) > 1;

2删除重复数据
DELETE FROM your_table_name WHERE Url IN (SELECT Url FROM tmp_table);

3删除零时表
DROP TABLE IF EXISTS tmp_table;