Question

考虑一个包含以下模式的表：

id, location, starred

有许多记录具有相同的位置：

id | location | starred
-----------------------
1     rome      yes
2     rome      no
3     rome      no
4     milan     yes
5     milan     no
6     bozen     no

我希望每个位置最多只有一条记录。考虑到主演唱片和非主演唱片之间的选择，我希望主演。那么sql会生成这个表：

id | location | starred
-----------------------
1     rome      yes
4     milan     yes
6     bozen     no

我怀疑这可以通过一些虚拟表或ªviews来完成。

DELETE FROM table
GROUP BY location,

Answer 1

使用分析功能删除重复项。下面的代码生成基于row_number的位置，并按星号desc排序（所以肯定是第一个）

 delete from mytable2 where id in ( 
select id from
( select  id, location,starred,row_number() over ( partition by location order by location, starred desc) row_num 
  from mytable2
) where row_num >1
)

Answer 2

如果[started]只能是yes或no，那么这应该有效：

create table data
(
id int identity(1,1),
location varchar(50),
[started] varchar(3)
)

insert into data select 'Rome', 'Yes'
insert into data select 'Rome', 'No'
insert into data select 'Rome', 'No'
insert into data select 'Milan', 'Yes'
insert into data select 'Milan', 'No'
insert into data select 'Bozen', 'No'

WITH locationsRanked (id, location, [started], rank)
AS
(
    select min(Id), location, [started],
    RANK() OVER (PARTITION BY location  ORDER BY location, [started] DESC) AS Rank
    from data
    group by location, [started]
)
select * from locationsRanked where Rank = 1
order by id

Answer 3

如果你只是想提取这样的数据应该有用：

select
    [table].*
from
    [table]
    inner join (select 
                    MIN(id) as id, 
                    location 
                from 
                    [table] 
                group by location) as data
        on [table].id = data.id

显然，您也可以使用此结果（或类似查询）来确定要删除的ID列表。

Answer 4

我认为这可以帮到你：

http://www.w3schools.com/sql/sql_distinct.asp

SQL删除具有一些常见字段值的重复记录？

4 个答案: