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SQLServer删除重复记录的几种方法

时间:2021-07-01 10:21:17 帮助过:28人阅读

例如: id name value 1 a pp 2 a pp 3 b iii 4 b pp 5 b pp 6 c pp 7 c pp 8 c iii id是主键 要求得到这样的结果 id name value 1 a pp 3 b iii 4 b pp 6 c pp 8 c iii 方法1 delete YourTable where [id] not in ( select max([id]) from YourTable group

  例如:

  id name value

  1 a pp

  2 a pp

  3 b iii

  4 b pp

  5 b pp

  6 c pp

  7 c pp

  8 c iii

  id是主键

  要求得到这样的结果

  id name value

  1 a pp

  3 b iii

  4 b pp

  6 c pp

  8 c iii

  方法1

  delete YourTable

  where [id] not in (

  select max([id]) from YourTable

  group by (name + value))

  方法2

  delete a

  from 表 a left join(

  select id=min(id) from 表 group by name,value

  )b on a.id=b.id

  where b.id is null

  查询及删除重复记录的SQL语句

  查询及删除重复记录的SQL语句

  1、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

  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、查找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、查找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(*) >; 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 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 tablename

  group by id

  having count(id) > 1

  )

  学习sql有一段时间了,发现在我建了一个用来测试的表(没有建索引)中出现了许多的重复记录。后来总结了一些删除重复记录的方法,在Oracle中,可以通过唯一rowid实现删除重复记录;还可以建临时表来实现...这个只提到其中的几种简单实用的方法,希望可以和大家分享(以表employee为例)。

  SQL> desc employee

  Name Null? Type

  ----------------------------------------- -------- ------------------

  emp_id NUMBER(10)

  emp_name VARCHAR2(20)

  salary NUMBER(10,2)

  可以通过下面的语句查询重复的记录:

  SQL> select * from employee;

  EMP_ID EMP_NAME SALARY

  ---------- ---------------------------------------- ----------

  1 sunshine 10000

  1 sunshine 10000

  2 semon 20000

  2 semon 20000

  3 xyz 30000

  2 semon 20000

  SQL> select distinct * from employee;

  EMP_ID EMP_NAME SALARY

  ---------- ---------------------------------------- ----------

  1 sunshine 10000

  2 semon 20000

  3 xyz 30000

  SQL> select * from employee group by emp_id,emp_name,salary having count (*)>1

  EMP_ID EMP_NAME SALARY

  ---------- ---------------------------------------- ----------

  1 sunshine 10000

  2 semon 20000

  SQL> select * from employee e1

  where rowid in (select max(rowid) from employe e2

  where e1.emp_id=e2.emp_id and

  e1.emp_name=e2.emp_name and e1.salary=e2.salary);

  EMP_ID EMP_NAME SALARY

  ---------- ---------------------------------------- ----------

  1 sunshine 10000

  3 xyz 30000

  2 semon 20000

  2. 删除的几种方法:

  (1)通过建立临时表来实现

  SQL>create table temp_emp as (select distinct * from employee)

  SQL> truncate table employee; (清空employee表的数据)

  SQL> insert into employee select * from temp_emp; (再将临时表里的内容插回来)

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