数据库里有一表LogFile 里面三个字段
ID, integer
EventTime,DateTime
EventContent,varchar(500)
现在我想删除数据库里的数据,让每天的记录只剩下一条(随便哪条都行) 这个该怎么做?
ID, integer
EventTime,DateTime
EventContent,varchar(500)
现在我想删除数据库里的数据,让每天的记录只剩下一条(随便哪条都行) 这个该怎么做?
delete a from LogFile a where
exists(select 1 from LogFile where convert(varchar(10),EventTime,120)=a.convert(varchar(10),EventTime,120) and ID>a.ID)
exists(select 1 from LogFile where convert(varchar(10),EventTime,120)=a.convert(varchar(10),EventTime,120) and ID>a.ID)
(
SELECT
rowno = ROW_NUMBER() OVER(PARTITION BY CONVERT(CHAR(10), EventTime, 120) ORDER BY EventTime DESC),
*
FROM tb
)
DELETE FROM cte
WHERE rowno <> 1
--> --> (Roy)生成測試數據if not object_id('Tempdb..#T') is null
drop table #T
Go
Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))
Insert #T
select 1,N'A',N'A1' union all
select 2,N'A',N'A2' union all
select 3,N'A',N'A3' union all
select 4,N'B',N'B1' union all
select 5,N'B',N'B2'
Go--I、Name相同ID最小的记录(推荐用1,2,3),保留最小一条
方法1:
delete a from #T a where exists(select 1 from #T where Name=a.Name and ID<a.ID)方法2:
delete a from #T a left join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null方法3:
delete a from #T a where ID not in (select min(ID) from #T where Name=a.Name)方法4(注:ID为唯一时可用):
delete a from #T a where ID not in(select min(ID)from #T group by Name)方法5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)>0方法6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID)方法7:
delete a from #T a where ID>any(select ID from #T where Name=a.Name)select * from #T生成结果:
/*
ID Name Memo
----------- ---- ----
1 A A1
4 B B1(2 行受影响)
*/
--II、Name相同ID保留最大的一条记录:方法1:
delete a from #T a where exists(select 1 from #T where Name=a.Name and ID>a.ID)方法2:
delete a from #T a left join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null方法3:
delete a from #T a where ID not in (select max(ID) from #T where Name=a.Name)方法4(注:ID为唯一时可用):
delete a from #T a where ID not in(select max(ID)from #T group by Name)方法5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)>0方法6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID desc)方法7:
delete a from #T a where ID<any(select ID from #T where Name=a.Name)
select * from #T
/*
ID Name Memo
----------- ---- ----
3 A A3
5 B B2(2 行受影响)
*/--3、删除重复记录没有大小关系时,处理重复值
--> --> (Roy)生成測試數據
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 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)
*/
数据库里有一表LogFile 里面三个字段
ID, integer
EventTime,DateTime
EventContent,varchar(500)
现在我想删除数据库里的数据,让每天的记录只剩下一条(随便哪条都行) 这个该怎么做?
----
delete A from (SELECT LogFile.*,ROW_NUMBER()OVER(PARTITION BY
cast(EventTime as date) ORDER BY cast(EventTime as date)) NUMBER
FROM LogFile ) A
where NUMBER>1测试:
USE STU_PLAN
GO
SELECT MY_PLAN.PLAN_ID,P_DATE,ROW_NUMBER()OVER(PARTITION BY
cast(P_DATE as date) ORDER BY cast(P_DATE as date)) NUMBER
FROM MY_PLAN
/*结果:
PLAN_ID P_DATE NUMBER
----------- ----------------------- --------------------
1005 2011-09-05 14:43:09.020 1
1006 2011-09-07 22:07:56.617 1
1007 2011-09-07 23:08:18.123 2
1010 2011-09-08 20:48:39.000 1
1011 2011-09-08 22:32:48.620 2
1012 2011-09-09 12:38:09.687 1
1013 2011-09-09 14:52:07.560 2(7 行受影响)
2楼方法有点瑕疵:把a.convert(varchar(10),EventTime,120)改成 convert(varchar(10),a.EventTime,120)即可3楼方法也有错误 如果将convert(varchar(10),a.eventtime,120)改为convert(varchar(10),t.eventtime,120),结果不符合我的要求,没有按照预想的那样去删除数据6楼方法可行11楼你的执行结果都不符合我的要求,所以没有测试过你给的代码