前言php
本文主要给你们介绍了关于MySQL中查询、删除重复记录的方法，分享出来供你们参考学习，下面来看看详细的介绍：mysql
查找全部重复标题的记录：sql
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1
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select
title,
count
(*)
as
count
from
user_table
group
by
title
having
count
>1;
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1
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SELECT
*
FROM
t_info a
WHERE
((
SELECT
COUNT
(*)
FROM
t_info
WHERE
Title = a.Title) > 1)
ORDER
BY
Title
DESC
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1、查找重复记录ide
一、查找所有重复记录post
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SELECT
*
FROM
t_info a
WHERE
((
SELECT
COUNT
(*)
FROM
t_info
WHERE
Title = a.Title) > 1)
ORDER
BY
Title
DESC
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二、过滤重复记录(只显示一条)学习
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Select
*
From
HZT
Where
ID
In
(
Select
Max
(ID)
From
HZT
Group
By
Title)
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注：此处显示ID最大一条记录spa
2、删除重复记录设计
一、删除所有重复记录（慎用）code
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Delete
表
Where
重复字段
In
(
Select
重复字段
From
表
Group
By
重复字段
Having
Count
(*)>1)
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二、保留一条（这个应该是大多数人所须要的 ^_^）blog
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Delete
HZT
Where
ID
Not
In
(
Select
Max
(ID)
From
HZT
Group
By
Title)
|
注：此处保留ID最大一条记录
3、举例
一、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断
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select
*
from
people
where
peopleId
in
(
select
peopleId
from
people
group
by
peopleId
having
count
(peopleId) > 1)
|
二、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录
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1
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delete
from
people
where
peopleId
in
(
select
peopleId
from
people
group
by
peopleId
having
count
(peopleId) > 1)
and
rowid
not
in
(
select
min
(rowid)
from
people
group
by
peopleId
having
count
(peopleId )>1)
|
三、查找表中多余的重复记录（多个字段）
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select
*
from
vitae a
where
(a.peopleId,a.seq)
in
(
select
peopleId,seq
from
vitae
group
by
peopleId,seq
having
count
(*) > 1)
|
四、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
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1
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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)
|
五、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
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1
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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)
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4、补充
有两个以上的重复记录，一是彻底重复的记录，也即全部字段均重复的记录，二是部分关键字段重复的记录，好比Name字段重复，而其余字段不必定重复或都重复能够忽略。
一、对于第一种重复，比较容易解决，使用
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select
distinct
*
from
tableName
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就能够获得无重复记录的结果集。
若是该表须要删除重复的记录（重复记录保留1条），能够按如下方法删除
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select
distinct
*
into
#Tmp
from
tableName
drop
table
tableName
select
*
into
tableName
from
#Tmp
drop
table
#Tmp
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发生这种重复的缘由是表设计不周产生的，增长惟一索引列便可解决。
二、这类重复问题一般要求保留重复记录中的第一条记录，操做方法以下
假设有重复的字段为Name,Address，要求获得这两个字段惟一的结果集
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select
identity(
int
,1,1)
as
autoID, *
into
#Tmp
from
tableName
select
min
(autoID)
as
autoID
into
#Tmp2
from
#Tmp
group
by
Name
,autoID
select
*
from
#Tmp
where
autoID
in
(
select
autoID
from
#tmp2)
|
总结
以上就是这篇文章的所有内容了，但愿本文的内容对你们的学习或者工做能带来必定的帮助
原文连接：http://blog.phpsoho.com/2017/06/20/mysql之-查询重复记录、删除重复记录方法大全/