MySQL查詢表內重複記錄

標籤：

 查詢及重複資料刪除記錄的方法
(一)
1、尋找表中多餘的重複記錄，重複記錄是根據單個欄位（peopleId）來判斷
select * from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

2、刪除表中多餘的重複記錄，重複記錄是根據單個欄位（peopleId）來判斷，只留有一個記錄
delete from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
and min(id) not in (select id from people group by peopleId having count(peopleId )>1)

3、尋找表中多餘的重複記錄（多個欄位）
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

4、刪除表中多餘的重複記錄（多個欄位），只留有rowid最小的記錄
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、尋找表中多餘的重複記錄（多個欄位），不包含rowid最小的記錄
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)

(二)
比方說
在A表中存在一個欄位“name”，
而且不同記錄之間的“name”值有可能會相同，
現在就是需要查詢出在該表中的各記錄之間，“name”值存在重複的項；
Select Name,Count(*) From A Group By Name Having Count(*) > 1

如果還查性別也相同大則如下:
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

(三)
方法一

declare @max integer,@id integer

declare cur_rows cursor local for select 主欄位,count(*) from 表名 group by 主欄位 having count(*) >； 1

open cur_rows

fetch cur_rows into @id,@max

while @@fetch_status=0

begin

select @max = @max -1

set rowcount @max

delete from 表名 where 主欄位 = @id

fetch cur_rows into @id,@max

end

close cur_rows

set rowcount 0

 

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MySQL查詢表內重複記錄