前言php
本文主要給你們介紹了關於MySQL中查詢、刪除重複記錄的方法，分享出來供你們參考學習，下面來看看詳細的介紹：mysql
查找全部重複標題的記錄：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
|
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、查找重複記錄ide
一、查找所有重複記錄post
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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
|
二、過濾重複記錄(只顯示一條)學習
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Select
*
From
HZT
Where
ID
In
(
Select
Max
(ID)
From
HZT
Group
By
Title)
|
注：此處顯示ID最大一條記錄spa
2、刪除重複記錄設計
一、刪除所有重複記錄（慎用）code
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Delete
表
Where
重複字段
In
(
Select
重複字段
From
表
Group
By
重複字段
Having
Count
(*)>1)
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二、保留一條（這個應該是大多數人所須要的 ^_^）blog
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1
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Delete
HZT
Where
ID
Not
In
(
Select
Max
(ID)
From
HZT
Group
By
Title)
|
注：此處保留ID最大一條記錄
3、舉例
一、查找表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷
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1
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select
*
from
people
where
peopleId
in
(
select
peopleId
from
people
group
by
peopleId
having
count
(peopleId) > 1)
|
二、刪除表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷，只留有rowid最小的記錄
|
1
|
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、查找表中多餘的重複記錄（多個字段）
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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)
|
四、刪除表中多餘的重複記錄（多個字段），只留有rowid最小的記錄
|
1
|
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、查找表中多餘的重複記錄（多個字段），不包含rowid最小的記錄
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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)
|
4、補充
有兩個以上的重複記錄，一是徹底重複的記錄，也即全部字段均重複的記錄，二是部分關鍵字段重複的記錄，好比Name字段重複，而其餘字段不必定重複或都重複能夠忽略。
一、對於第一種重複，比較容易解決，使用
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1
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select
distinct
*
from
tableName
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就能夠獲得無重複記錄的結果集。
若是該表須要刪除重複的記錄（重複記錄保留1條），能夠按如下方法刪除
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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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發生這種重複的緣由是表設計不周產生的，增長惟一索引列便可解決。
二、這類重複問題一般要求保留重複記錄中的第一條記錄，操做方法以下
假設有重複的字段爲Name,Address，要求獲得這兩個字段惟一的結果集
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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)
|
總結
以上就是這篇文章的所有內容了，但願本文的內容對你們的學習或者工做能帶來必定的幫助
原文連接：http://blog.phpsoho.com/2017/06/20/mysql之-查詢重複記錄、刪除重複記錄方法大全/