如何去掉ResourceName列的重复字段
select
A.ResourceId
,left(ResourceName,8) as ResourceName
,A.RealPrice
,dbo.Resource_GetResourceImageFileName(A.ResourceId) AS FileName
, A.CreateTime
from
Resource_Resources A where (left(isnull((select Code from Resource_Categories where ResourceCategoryId = A.ResourceCategoryId),''),3) = 002)
and A.IsVerified = 3
order by A.CreateTime desc
谢谢,
select
A.ResourceId
,left(ResourceName,8) as ResourceName
,A.RealPrice
,dbo.Resource_GetResourceImageFileName(A.ResourceId) AS FileName
, A.CreateTime
from
Resource_Resources A where (left(isnull((select Code from Resource_Categories where ResourceCategoryId = A.ResourceCategoryId),''),3) = 002)
and A.IsVerified = 3
order by A.CreateTime desc
谢谢,
有两个意义上的重复记录,一是完全重复的记录,也即所有字段均重复的记录,二是部分关键字段重复的记录,比如Name字段重复,而其他字段不一定重复或都重复可以忽略。
1、对于第一种重复,比较容易解决,使用
select distinct * from tableName
就可以得到无重复记录的结果集。
如果该表需要删除重复的记录(重复记录保留1条),可以按以下方法删除
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
发生这种重复的原因是表设计不周产生的,增加唯一索引列即可解决。
2、这类重复问题通常要求保留重复记录中的第一条记录,操作方法如下
假设有重复的字段为Name,Address,要求得到这两个字段唯一的结果集
select identity(int,1,1) as autoID, * into #Tmp from tableName
select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID
select * from #Tmp where autoID in(select autoID from #tmp2)
最后一个select即得到了Name,Address不重复的结果集(但多了一个autoID字段,实际写时可以写在select子句中省去此列)
假如我有一列为
1,3,4,5,6,7,8,9
2,3,6,7,9,0,-,1我们就当第2列是ResourceName,我们去掉重复列,我们取第一行还是取第二行?
alter table Resource_Resources add seq int identity(1,1)
delete from Resource_Resources where seq not in (select max(seq) seq from Resource_Resources group by ResourceName)
alter table Resource_Resources drop column seq
select * from Resource_Resources
delete from Resource_Resources where seq not in (select max(seq) seq from Resource_Resources group by ResourceName)
alter table Resource_Resources drop column seq
select * from Resource_Resources
试试
很多个字段重复用 distinct
可以提高效率
select top 10
C.ResourceId
,B.ResourceName
,C.RealPrice
,dbo.Resource_GetResourceImageFileName(C.ResourceId) AS FileName
FROM
(
select MAX(A.ResourceId)AS ResourceId,A.ResourceName from
(
select ResourceId,
SUBSTRING(ResourceName, 1,
case
when LEN(ResourceName)>5 then LEN(ResourceName)-4
when LEN(ResourceName)>3 then LEN(ResourceName)-3
else LEN(ResourceName) end) as ResourceName
from dbo.Resource_Resources
) A group by A.ResourceName
) B
INNER JOIN dbo.Resource_Resources C ON B.ResourceId = C.ResourceIdwhere (left(isnull((select Code from Resource_Categories where ResourceCategoryId = C.ResourceCategoryId),''),3) = 002)
and C.IsVerified = 3
order by C.CreateTime desc