--1. 刪除已存在表.
if exists (
select 1 from sysobjects where id = object_id(n'test') and objectproperty(id, n'isusertable') = 1
) begin
drop table test
end
go--2. 建表
create table [dbo].test( [userid] [int] not null, [name] varchar(20) not null,isenabled bit)
goinsert into dbo.test
select 1,'aa',0 union all --注：只能用 union, 不能用 union all. 要不只會有一條記錄
select 1,'aa',1 union all
select 2,'bb',0 union all
select 2,'bb',0 union all
select 2,'cc',1 union all
select 3,'dd',0
go--如果有檢視先刪除
if exists(select 1 from sys.views where name='tmp_view_test')
drop view tmp_view_test
go--建立檢視 (注：partition by的功能為以***列來分組， 有點相當於group by)
--盡可能刪除 isenabled = 0 的記錄
create view tmp_view_test as
select row_number() over(partition by [userid] order by isnull(isenabled,0) desc) as num,*
from test
go--刪除前情況
select * from tmp_view_test order by userid,num
--刪除重複
delete from tmp_view_test where num!=1
--刪除後情況
select * from tmp_view_test order by userid,num
不用檢視刪除：
--1. 刪除已存在表.
if object_id(n'test') is not null
begin
drop table test
end
go--2. 建表
create table [dbo].test( [userid] [int] not null, [name] varchar(20) not null,isenabled bit)
goset nocount on
insert into dbo.test
select 1,'aa',0 union all --注：只能用 union, 不能用 union all. 要不只會有一條記錄
select 1,'aa',1 union all
select 2,'bb',0 union all
select 2,'bb',0 union all
select 2,'cc',1 union all
select 3,'dd',0
goselect * from test
/*userid name isenabled
1 aa 0
1 aa 1
2 bb 0
2 bb 0
2 cc 1
3 dd 0
*/delete from tmp from
(select row_number() over (partition by userid order by isenabled desc) as rid,* from test) as tmp
where rid!=1
select * from test
/*userid name isenabled
1 aa 1
2 cc 1
3 dd 0
*/
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