mysql怎样实现查重只留一个

mysql实现查重只留一个的办法：第一通过“select*from”查寻表中余外的反复记载；然后通过“deletefrom”删除反复数据，并只保存一个数据即可。

mysql实现查重只留一个的办法：第一通过“select * from”查寻表中余外的反复记载；然后通过“delete from”删除反复数据，并只保存一个数据即可。

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mysql 删除反复数据只保存一笔记录

删除反复数据保存name中id最小的记载

delete from order_info where id not in (select id from (select min(id) as id from order_info group by order_number) as b);

delete from table where id not in (select min(id) from table group by name having count(name)>1) and  id in (select id group by name having count(name)>1)

(注意：HAVING 子句对 GROUP BY 子句设定前提的方式与 WHERE 和 SELECT 的交互方式相似。WHERE 搜寻前提在进行分组操纵以前利用；而 HAVING 搜寻前提在进行分组操纵之后利用。HAVING 语法与 WHERE 语法相似，但 HAVING 可以包括聚合函数。HAVING 子句可以援用选中列表中显示的任意项。)

扩展：

SQL：删除反复数据，只保存一条用SQL语句,删除掉反复项只保存一条在几千笔记录里,存在着些雷同的记载,怎样能用SQL语句,删除掉反复的呢

1、查寻表中余外的反复记载，反复记载是依据单个字段（peopleId）来推断

select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

2、删除表中余外的反复记载，反复记载是依据单个字段（peopleId）来推断，只留有rowid最小的记载

delete from people where   peopleName in (select peopleName    from people group by peopleName      having count(peopleName) > 1) and   peopleId not in (select min(peopleId) from people group by peopleName     having count(peopleName)>1)

3、查寻表中余外的反复记载（多个字段）

select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

4、删除表中余外的反复记载（多个字段），只留有rowid最小的记载

delete from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

5、查寻表中余外的反复记载（多个字段），不包括rowid最小的记载

select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

6.消弭一个字段的左边的首先位：

update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like '村%'

7.消弭一个字段的右侧的首先位：

update tableName set [Title]=left([Title],(len([Title])-1)) where Title like '%村'

8.假删除表中余外的反复记载（多个字段），不包括rowid最小的记载

update vitae set ispass=-1 where peopleId in (select peopleId from vitae group by peopleId,seq having count(*) > 1) and seq in （select seq from vitae group by peopleId,seq having count(*) > 1） and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

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