mysql查询相同字段值的个数_MySQL根据某⼀个或者多个字
段查重复数据的sql语句...
sql 查出⼀张表中重复的所有记录数据
1.表中有id和name 两个字段，查询出name重复的所有数据
select * from xi a where (a.username) in (select username from xi group by username having count(*) > 1)
2、查询出所有数据进⾏分组之后，和重复数据的重复次数的查询数据，先列下：
select count(username) as '重复次数',username from xi group by username having count(*)>1 order by username desc
3、⼀下为 查看别⼈的 结果，现列下：查询及删除重复记录的⽅法⼤全
1、查表中多余的重复记录，重复记录是根据单个字段(peopleId)来判断
select * from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
2、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
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、查表中多余的重复记录(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、删除表中多余的重复记录(多个字段)，只留有rowid最⼩的记录
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、查表中多余的重复记录(多个字段)，不包含rowid最⼩的记录
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)
⽐⽅说
在A表中存在⼀个字段“name”，
⽽且不同记录之间的“name”值有可能会相同，
现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；
Select Name,Count(*) From A Group By Name Having Count(*) > 1
如果还查性别也相同⼤则如下:
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 主字段,count(*) from 表名 group by 主字段 having count(*) >;
open cur_rows fetch cur_rows into @id,@maxwhile @@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,@maxend
close cur_rows
set rowcount 0
⽅法⼆＂重复记录＂有两个意义上的重复记录，⼀是完全重复的记录，也即所有字段均重复的记录，⼆是部分关键字段重复的记录，⽐如Name字段重复，⽽其他字段不⼀定重复或都重复可以忽略。
1、对于第⼀种重复，⽐较容易解决，使⽤
select distinct * from tableName
就可以得到⽆重复记录的结果集。
如果该表需要删除重复的记录(重复记录保留1条)，
可以按以下⽅法删除
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
发⽣这种重复的原因是表设计不周产⽣的，增加唯⼀索引列即可解决。
2、这类重复问题通常要求保留重复记录中的第⼀条记录，操作⽅法如下  假设有重复的字段为Name,Address，要求得到这两个字段唯⼀的结果集
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)
最后⼀个select即得到了Name，Address不重复的结果集(但多了⼀个autoID字段，实际写时可以写在select⼦句中省去此列)
(四)查询重复
select * from tablename where id in (select id from tablenamegroup by idhaving count(id) > 1)
对⼀个字段查重复记录
根据sample_code字段到重复记录
SELECT * FROM tb_table WHERE sample_code IN( SELECT sample_code FROM tb_table GROUP BY sample_code HAVING COUNT(sample_code) > 1 );
对多个字段查重复记录(这⾥以2个为例)
mysql删除重复的数据保留一条
根据name和code字段到重复记录
SELECT * from (SELECT *, CONCAT(name,code) as nameAndCode from tb_table) t WHERE t.nameAndCode in
(
SELECT nameAndCode from (SELECT CONCAT(name,code) as nameAndCode from tb_table) tt GROUP BY nameAndCode HAVING count(nameAndCode) > 1
)
总结
以上所述是⼩编给⼤家介绍的MySQL根据某⼀个或者多个字段查重复数据的sql语句，希望对⼤家有所帮助，如果⼤家有任何疑问请给我留⾔，⼩编会及时回复⼤家的。在此也⾮常感谢⼤家对脚本之家⽹站的⽀持！

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