SELECT distinct EmployeeId from DinnerCollect where Date='2009-06-24' and Time>'16:40'
上面语句出错,“ntext 数据类型不能选为 DISTINCT,因为它不可比。”
SELECT * from DinnerCollect where Date='2009-06-24' and Time>'16:40'
会有一些多余的记录。EmployeeId 这个字段同一个值都会出现两笔(但是两笔有一个字段不一样,是系统自动生成的一个字段,其他字段完全一样,任意删除一笔就可以),需删除一笔。谢谢各位大虾
上面语句出错,“ntext 数据类型不能选为 DISTINCT,因为它不可比。”
SELECT * from DinnerCollect where Date='2009-06-24' and Time>'16:40'
会有一些多余的记录。EmployeeId 这个字段同一个值都会出现两笔(但是两笔有一个字段不一样,是系统自动生成的一个字段,其他字段完全一样,任意删除一笔就可以),需删除一笔。谢谢各位大虾
--> --> (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)
*/
SELECT * from DinnerCollect a where Date='2009-06-24' and Time>'16:40'
and not exists(select 1 from dinnercollect where EmployeeId =a.EmployeeId and 主键>a.主键)
where exists (select 1 from DinnerCollect where EmployeeId=a.EmployeeId and Date>a.Date)
select t.* from DinnerCollect t where Date = (select min(Date) from DinnerCollect where EmployeeId = t.EmployeeId)
select t.* from DinnerCollect t where not exists (select 1 from DinnerCollect where EmployeeId = t.EmployeeId and date < t.date)select t.* from DinnerCollect t where Date = (select max(Date) from DinnerCollect where EmployeeId = t.EmployeeId)
select t.* from DinnerCollect t where not exists (select 1 from DinnerCollect where EmployeeId = t.EmployeeId and date > t.date)
where Date='2009-06-24' and Time>'16:40' select t.* from DinnerCollect t where where Date='2009-06-24' and Time>'16:40' and Date = (select min(Date) from DinnerCollect where Date='2009-06-24' and Time>'16:40' and EmployeeId = t.EmployeeId )
select t.* from DinnerCollect t where Date='2009-06-24' and Time>'16:40' and not exists (select 1 from DinnerCollect where Date='2009-06-24' and Time>'16:40' and EmployeeId = t.EmployeeId and date < t.date) select t.* from DinnerCollect t where Date='2009-06-24' and Time>'16:40' and Date = (select max(Date) from DinnerCollect where Date='2009-06-24' and Time>'16:40' and EmployeeId = t.EmployeeId)
select t.* from DinnerCollect t where Date='2009-06-24' and Time>'16:40' and not exists (select 1 from DinnerCollect where Date='2009-06-24' and Time>'16:40' and EmployeeId = t.EmployeeId and date > t.date)