表的結構可以理解為：
類型 日期 備注
nokia 20090214 aa
nokia 20090215 bb
nokia 20090225 cc
nokia 20090218 dd
LG 20090225 cc
MOTO 20090218 dd
表中數據類型有可能重復，
時間字段為：相同類型則不重復，不同類型則有可能重復。
時間越靠后表明數據越新
如何查詢出所有類型的最新記錄
我寫了個SQL
是這樣的
- SQL code
-
select * from table where 日期 in (selcet max (日期) from table group by 類型)
可是DT的是 Nokia 的更新時間中有20090225這條記錄，這條記錄不是Nokia的最新記錄，但是卻因為LG這個類型里面也有20090225這個時間。
所以結果里面出現了兩條Nokia的記錄。
不知道我把問題表述的清楚沒有。求指教怎么修改語句。
Beirut Replied at : 2012-02-14 11:01:14
- SQL code
-
select * from table t where 日期 = (selcet max (日期) from table where 類型 = t.類型)
Beirut Replied at : 2012-02-14 11:01:30
- SQL code
-
-- 處理表重復記錄(查詢和刪除) /* ***************************************************************************************************************************************************** 1、Num、Name相同的重復值記錄,沒有大小關系只保留一條 2、Name相同,ID有大小關系時,保留大或小其中一個記錄 整理人：中國風(Roy) 日期:2008.06.06 ***************************************************************************************************************************************************** */ -- 1、用於查詢重復處理記錄(如果列沒有大小關系時2000用生成自增列和臨時表處理,SQL2005用row_number函數處理) -- > --> (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最小的記錄(推薦用1,2,3),方法3在SQl05時，效率高於1、2 方法1: Select * from #T a where not exists ( select 1 from #T where Name = a.Name and ID < a.ID) 方法2: select a. * from #T a join ( select min (ID)ID,Name from #T group by Name) b on a.Name = b.Name and a.ID = b.ID 方法3: select * from #T a where ID = ( select min (ID) from #T where Name = a.Name) 方法4: select a. * from #T a join #T b on a.Name = b.Name and a.ID >= b.ID group by a.ID,a.Name,a.Memo having count ( 1 ) = 1 方法5: select * from #T a group by ID,Name,Memo having ID = ( select min (ID) from #T where Name = a.Name) 方法6: select * from #T a where ( select count ( 1 ) from #T where Name = a.Name and ID < a.ID) = 0 方法7: select * from #T a where ID = ( select top 1 ID from #T where Name = a.name order by ID) 方法8: select * from #T a where ID !>all ( select ID from #T where Name = a.Name) 方法9(注:ID為唯一時可用): select * from #T a where ID in ( select min (ID) from #T group by Name) -- SQL2005: 方法10: select ID,Name,Memo from ( select * , min (ID) over (partition by Name) as MinID from #T a)T where ID = MinID 方法11: select ID,Name,Memo from ( select * ,row_number() over (partition by Name order by ID) as MinID from #T a)T where MinID = 1 生成結果: /* ID Name Memo ----------- ---- ---- 1 A A1 4 B B1 (2 行受影響) */ -- II、Name相同ID最大的記錄,與min相反: 方法1: Select * from #T a where not exists ( select 1 from #T where Name = a.Name and ID > a.ID) 方法2: select a. * from #T a join ( select max (ID)ID,Name from #T group by Name) b on a.Name = b.Name and a.ID = b.ID order by ID 方法3: select * from #T a where ID = ( select max (ID) from #T where Name = a.Name) order by ID 方法4: select a. * from #T a join #T b on a.Name = b.Name and a.ID <= b.ID group by a.ID,a.Name,a.Memo having count ( 1 ) = 1 方法5: select * from #T a group by ID,Name,Memo having ID = ( select max (ID) from #T where Name = a.Name) 方法6: select * from #T a where ( select count ( 1 ) from #T where Name = a.Name and ID > a.ID) = 0 方法7: select * from #T a where ID = ( select top 1 ID from #T where Name = a.name order by ID desc ) 方法8: select * from #T a where ID !<all ( select ID from #T where Name = a.Name) 方法9(注:ID為唯一時可用): select * from #T a where ID in ( select max (ID) from #T group by Name) -- SQL2005: 方法10: select ID,Name,Memo from ( select * , max (ID) over (partition by Name) as MinID from #T a)T where ID = MinID 方法11: select ID,Name,Memo from ( select * ,row_number() over (partition by Name order by ID desc ) as MinID from #T a)T where MinID = 1 生成結果2: /* ID Name Memo ----------- ---- ---- 3 A A3 5 B B2 (2 行受影響) */ -- 2、刪除重復記錄有大小關系時,保留大或小其中一個記錄 -- > --> (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最小的記錄(推薦用1,2,3),保留最小一條 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為唯一時可用): 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 生成結果: /* ID Name Memo ----------- ---- ---- 1 A A1 4 B B1 (2 行受影響) */ -- II、Name相同ID保留最大的一條記錄: 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為唯一時可用): 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 行受影響) */ -- 3、刪除重復記錄沒有大小關系時，處理重復值 -- > --> (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 -- 排除重復記錄結果集生成臨時表# truncate table #T -- 清空表 insert #T select * from # -- 把臨時表#插入到表#T中 -- 查看結果 select * from #T /* Num Name ----------- ---- 1 A 2 B (2 行受影響) */ -- 重新執行測試數據后用方法2 方法2: alter table #T add ID int identity -- 新增標識列 go delete a from #T a where exists ( select 1 from #T where Num = a.Num and Name = a.Name and ID > a.ID) -- 只保留一條記錄 go alter table #T drop column ID -- 刪除標識列 -- 查看結果 select * from #T /* Num Name ----------- ---- 1 A 2 B (2 行受影響) */ -- 重新執行測試數據后用方法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 -- 查看結果 select * from #T /* Num Name ----------- ---- 1 A 2 B (2 行受影響) */
lhqdyy9 Replied at : 2012-02-14 11:01:52
select * from table A where 日期 in(selcet max(日期) from table B where B.類型 = A.類型 group by 類型)
angognda Replied at : 2012-02-14 11:11:43
- SQL code
-
select * from table A where 日期 in (selcet max (日期) from table B where B.類型 = A.類型 group by 類型)
TravyLee Replied at : 2012-02-14 11:59:16
select*from(select *，row_number()over(partition by 型號 order by 日期desc) as num from table)b where num=1
TravyLee Replied at : 2012-02-14 12:25:49
/*
問題描述：
表的結構可以理解為：
類型 日期 備注
nokia 20090214 aa
nokia 20090215 bb
nokia 20090225 cc
nokia 20090218 dd
LG 20090225 cc
MOTO 20090218 dd
表中數據類型有可能重復，
時間字段為：相同類型則不重復，不同類型則有可能重復。
時間越靠后表明數據越新
如何查詢出所有類型的最新記錄
*/
go
if object_id('tbl')is not null
drop table tbl
go
create table tbl(
類型 varchar(10),
日期 datetime,
備注 varchar(20)
)
go
insert tbl
select 'nokia','20090214','aa' union all
select 'nokia','20090215','bb' union all
select 'nokia','20090225','cc' union all
select 'nokia','20090218','dd' union all
select 'LG','20090225','cc' union all
select 'MOTO','20090218','ee' union all
select 'LG','20090720','ff' union all
select 'MOTO','20090514','gg'
select 類型,日期,備注 from
(select *,
ROW_NUMBER()over(partition by 類型 order by 日期 desc) as num
from tbl)b where num=1 order by 備注
/*
類型 日期 備注
nokia 2009-02-25 00:00:00.000 cc
LG 2009-07-20 00:00:00.000 ff
MOTO 2009-05-14 00:00:00.000 gg
*/
問題描述：
表的結構可以理解為：
類型 日期 備注
nokia 20090214 aa
nokia 20090215 bb
nokia 20090225 cc
nokia 20090218 dd
LG 20090225 cc
MOTO 20090218 dd
表中數據類型有可能重復，
時間字段為：相同類型則不重復，不同類型則有可能重復。
時間越靠后表明數據越新
如何查詢出所有類型的最新記錄
*/
go
if object_id('tbl')is not null
drop table tbl
go
create table tbl(
類型 varchar(10),
日期 datetime,
備注 varchar(20)
)
go
insert tbl
select 'nokia','20090214','aa' union all
select 'nokia','20090215','bb' union all
select 'nokia','20090225','cc' union all
select 'nokia','20090218','dd' union all
select 'LG','20090225','cc' union all
select 'MOTO','20090218','ee' union all
select 'LG','20090720','ff' union all
select 'MOTO','20090514','gg'
select 類型,日期,備注 from
(select *,
ROW_NUMBER()over(partition by 類型 order by 日期 desc) as num
from tbl)b where num=1 order by 備注
/*
類型 日期 備注
nokia 2009-02-25 00:00:00.000 cc
LG 2009-07-20 00:00:00.000 ff
MOTO 2009-05-14 00:00:00.000 gg
*/
TravyLee Replied at : 2012-02-14 12:28:33