表的结构可以理解为：
类型 日期 备注
nokia 20090214 aa
nokia 20090215 bb
nokia 20090225 cc
nokia 20090218 dd
LG 20090225 cc
MOTO 20090218 dd
表中数据类型有可能重复，
时间字段为：相同类型则不重复，不同类型则有可能重复。
时间越靠后表明数据越新
如何查询出所有类型的最新记录
我写了个SQL
是这样的
- SQL code
-
select * from table where 日期 in (selcet max (日期) from table group by 类型)
可是DT的是 Nokia 的更新时间中有20090225这条记录，这条记录不是Nokia的最新记录，但是却因为LG这个类型里面也有20090225这个时间。
所以结果里面出现了两条Nokia的记录。
不知道我把问题表述的清楚没有。求指教怎么修改语句。
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 类型 = t.类型)
Beirut Replied at : 2012-02-14 11:01:30
- SQL code
-
-- 处理表重复记录(查询和删除) /* ***************************************************************************************************************************************************** 1、Num、Name相同的重复值记录,没有大小关系只保留一条 2、Name相同,ID有大小关系时,保留大或小其中一个记录 整理人：中国风(Roy) 日期:2008.06.06 ***************************************************************************************************************************************************** */ -- 1、用于查询重复处理记录(如果列没有大小关系时2000用生成自增列和临时表处理,SQL2005用row_number函数处理) -- > --> (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最小的记录(推荐用1,2,3),方法3在SQl05时，效率高于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为唯一时可用): 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 生成结果: /* ID Name Memo ----------- ---- ---- 1 A A1 4 B B1 (2 行受影响) */ -- II、Name相同ID最大的记录,与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为唯一时可用): 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 生成结果2: /* ID Name Memo ----------- ---- ---- 3 A A3 5 B B2 (2 行受影响) */ -- 2、删除重复记录有大小关系时,保留大或小其中一个记录 -- > --> (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) */
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.类型 = A.类型 group by 类型)
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.类型 = A.类型 group by 类型)
TravyLee Replied at : 2012-02-14 11:59:16
select*from(select *，row_number()over(partition by 型号 order by 日期desc) as num from table)b where num=1
TravyLee Replied at : 2012-02-14 12:25:49
/*
问题描述：
表的结构可以理解为：
类型 日期 备注
nokia 20090214 aa
nokia 20090215 bb
nokia 20090225 cc
nokia 20090218 dd
LG 20090225 cc
MOTO 20090218 dd
表中数据类型有可能重复，
时间字段为：相同类型则不重复，不同类型则有可能重复。
时间越靠后表明数据越新
如何查询出所有类型的最新记录
*/
go
if object_id('tbl')is not null
drop table tbl
go
create table tbl(
类型 varchar(10),
日期 datetime,
备注 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 类型,日期,备注 from
(select *,
ROW_NUMBER()over(partition by 类型 order by 日期 desc) as num
from tbl)b where num=1 order by 备注
/*
类型 日期 备注
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
*/
问题描述：
表的结构可以理解为：
类型 日期 备注
nokia 20090214 aa
nokia 20090215 bb
nokia 20090225 cc
nokia 20090218 dd
LG 20090225 cc
MOTO 20090218 dd
表中数据类型有可能重复，
时间字段为：相同类型则不重复，不同类型则有可能重复。
时间越靠后表明数据越新
如何查询出所有类型的最新记录
*/
go
if object_id('tbl')is not null
drop table tbl
go
create table tbl(
类型 varchar(10),
日期 datetime,
备注 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 类型,日期,备注 from
(select *,
ROW_NUMBER()over(partition by 类型 order by 日期 desc) as num
from tbl)b where num=1 order by 备注
/*
类型 日期 备注
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