《Mysql入門SQL重復記錄查詢 查詢多個字段、多表查詢、刪除重復記錄的方法》要點：
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SQL重復記錄查詢MYSQL教程
1、查找表中多余的重復記錄,重復記錄是根據單個字段(peopleId)來判斷?
MYSQL教程
select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
例二：?
MYSQL教程
select * from testtable where numeber in (select number from people group by number having count(number) > 1 )
可以查出testtable表中number相同的記錄??
MYSQL教程
2、刪除表中多余的重復記錄,重復記錄是根據單個字段(peopleId)來判斷,只留有rowid最小的記錄?
MYSQL教程
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)
3、查找表中多余的重復記錄(多個字段)??
MYSQL教程
select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
4、刪除表中多余的重復記錄(多個字段),只留有rowid最小的記錄?
MYSQL教程
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、查找表中多余的重復記錄(多個字段),不包含rowid最小的記錄?
MYSQL教程
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)?MYSQL教程
比方說?MYSQL教程
在A表中存在一個字段“name”,?MYSQL教程
而且不同記錄之間的“name”值有可能會相同,?MYSQL教程
現在就是需要查詢出在該表中的各記錄之間,“name”值存在重復的項；?
MYSQL教程
Select Name,Count(*) From A Group By Name Having Count(*) > 1
如果還查性別也相同大則如下：?
MYSQL教程
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1
(三)?MYSQL教程
辦法一?MYSQL教程
declare @max integer,@id integer declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 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 主字段 = @id fetch cur_rows into @id,@max end close cur_rows set rowcount 0
辦法二??
MYSQL教程
有兩個意義上的重復記錄,一是完全重復的記錄,也即所有字段均重復的記錄,二是部分關鍵字段重復的記錄,比如Name字段重復,而其他字段不一定重復或都重復可以忽略.??
MYSQL教程
1、對于第一種重復,比較容易解決,使用?
MYSQL教程
select distinct * from tableName
就可以得到無重復記錄的結果集.??
MYSQL教程
如果該表需要刪除重復的記錄(重復記錄保留1條),可以按以下辦法刪除?
MYSQL教程
select distinct * into #Tmp from tableName drop table tableName select * into tableName from #Tmp drop table #Tmp
發生這種重復的原因是表設計不周產生的,增加唯一索引列即可解決.??
MYSQL教程
2、這類重復問題通常要求保留重復記錄中的第一條記錄,操作辦法如下??
MYSQL教程
假設有重復的字段為Name,Address,要求得到這兩個字段唯一的結果集?
MYSQL教程
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)
最后一個select即得到了Name,Address不重復的結果集(但多了一個autoID字段,實際寫時可以寫在select子句中省去此列)??
MYSQL教程
(四)??
MYSQL教程
查詢重復?
MYSQL教程
select * from tablename where id in ( select id from tablename group by id having count(id) > 1 )
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