[英]SQL Compressing Table - Removing Like Items
有一个包含ID,IDLicense,Brand和ExtraBrands的表
尝试通过IDLicense抓取所有类似的记录来合并所有记录,方法是获取IDLicense的所有副本,删除所有副本,但保留品牌名称并将其添加到原始IDLicense,然后将已删除副本的品牌添加到ExtraBrands。
到目前为止,我已经能够选择所有具有重复项的IDLicense。 使用临时表存储所有其他信息。
INSERT INTO #TempTable (ID, IDLicense, Brand, ExtraBrands)
SELECT ID, IDLicense, Brand, ExtraBrands FROM BrandOrders
WHERE IDLicense IN (SELECT IDLicense FROM BrandOrders GROUP BY IDLicense HAVING COUNT(*) > 1)
是一种简单的方法,而不是在此处使用临时表来删除所有相似的数据并从副本中获取品牌并将其添加为ExtraBrands? 然后删除重复项。
数据示例:
下表:
1. IdLicense = 1, Brand="BlueBird", ExtraBrands is null
2. IdLicense = 1, Brand="RedBird", ExtraBrands is null
3. IdLicense = 1, Brand="YellowBird", ExtraBrands is null
4. IdLicense = 2, Brand="BlueBird", ExtraBrands is null
5. IdLicense = 2, Brand="RedBird", ExtraBrands is null
最后应将其全部压缩为
1. IdLicense = 1, Brand="BlueBird", ExtraBrands = "RedBird YellowBird"
2. IdLicense = 2, Brand="BlueBird", ExtraBrands = "RedBird"
您可以使用下面的代码执行所需的操作,但是我建议您不要对数据库进行这种非规范化。 在单个列中存储多个离散值会破坏关系模型,并经常导致各种问题。
相反,我建议您对表进行规范化,并使用如下所示的模式,在该表中,有一个连接表,用于将许可实体与品牌实体连接起来:
CREATE TABLE BrandOrders (IdLicense int primary key);
CREATE TABLE Brands (BrandID int primary key, Brand varchar(20));
CREATE TABLE LicenseBrands (
IdLicense int foreign key references BrandOrders,
BrandID int foreign key references Brands,
MainBrand bit,
PRIMARY KEY (IdLicense, BrandId)
);
这样既可以确保数据完整性,又可以节省空间,并且使用起来也容易得多。
话虽如此,这是查询(更新,然后删除)以“修复”您的数据:
;with cte as (
select *, r=row_number() over (partition by idlicense order by id)
from brandorders
where idlicense in (
select idlicense from brandorders group by idlicense having count(*) > 1
)
)
update extern
set extrabrands = left(c , len(c)-1)
from cte extern
cross apply
(
select brand + ','
from cte as intern
where extern.idlicense = intern.idlicense and r > 1
for xml path('')
) extrabrands (c)
where extern.r = 1;
delete from brandorders
where idlicense in (
select idlicense from brandorders group by idlicense having count(*) > 1
)
and extrabrands is null;
执行后的结果将是您的数据如下所示:
ID IdLicense Brand ExtraBrands
1 1 BlueBird RedBird,YellowBird
4 2 BlueBird RedBird
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