sql删除重复记录没有大小关系时重复值的处理方法

sql 删除重复记录没有大小关系时，重复值将如何处理呢？ 下文就将为您介绍sql删除重复记录没有大小关系时重复值的处理方法，供您参考，希望对您有所启迪。

–> –> (roy)生成

if not object_id(tempdb..#t) is null
    drop table #t
go
create table #t([num] int,[name] nvarchar(1))
insert #t
select 1,na union all
select 1,na union all
select 1,na union all
select 2,nb union all
select 2,nb
go方法1:

if object_id(tempdb..#) is not null
    drop table #
select distinct * into # from #t–排除重复记录结果集生成临时表#

truncate table #t–清空表

insert #t select * from #    –把临时表#插入到表#t中
–查看结果
select * from #t

/*
num         name
———– —-
1           a
2           b

(2 行受影响)#p#
*/

–重新执行测试数据后用方法2
方法2:

alter table #t add id int identity–新增标识列
go
delete a from  #t a where  exists(select 1 from #t where num=a.num and name=a.name and id>a.id)–只保留一条记录
go
alter table #t drop column id–删除标识列–查看结果
select * from #t

/*
num         name
———– —-
1           a
2           b

(2 行受影响)

*/

–重新执行测试数据后用方法3
方法3:

declare roy_cursor cursor local for#p#
select count(1)-1,num,name from #t group by num,name having count(1)>1
declare @con int,@num int,@name nvarchar(1)
open roy_cursor
fetch next from roy_cursor into @con,@num,@name
while @@fetch_status=0
begin
    set rowcount @con;
    delete #t where num=@num and name=@name
    set rowcount 0;
    fetch next from roy_cursor into @con,@num,@name
end
close roy_cursor
deallocate roy_cursor–查看结果
select * from #t
/*
num         name
———– —-
1           a
2           b

(2 行受影响)
*/
//利用存储过程

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//使用函数

select distinct * into #tmp from tablename
drop table tablename
select * into tablename from #tmp
drop table #tmp

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