sql 删除重复记录没有大小关系时，处理重复值

sql 删除重复记录没有大小关系时，处理重复值

sql 删除重复记录没有大小关系时，处理重复值

--> --> (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,n'a' union all
select 1,n'a' union all
select 1,n'a' union all
select 2,n'b' union all
select 2,n'b'
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)
*/

--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
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 and
    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

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