SQL SELECT加入字符串集ID

Question

我不得不面对一个MSSQL数据库，并在表中给出这样的信息：

Users: 

ID Name Countries 
-------------------- 
1 User1 1,2,3 
2 User2 2,5 

Countries: 
ID Country 
---------- 
1 Australia 
2 Germany 
3 USA 
4 Norway 
5 Canada 

现在，我所寻找的是一个select语句，这将使我喜欢这样的结果：

Result: 
ID User CountriesByName 
----------------------------- 
1 User1 Australia, Germany, USA 
2 User2 Germany, Canada 

我宁愿不会依赖于特殊的MSSQL语法在一些特殊的解决方案，但没有办法，我用一些LINQ魔法:(

Answer 1

首先，您需要将该字符串分开。这里是一个可行的分裂功能：

Create Function [dbo].[split] 
    (@input varChar(8000)  -- List of delimited items 
    ,@delimit varChar(8000) = ',') -- delimiter that separates items 
Returns @List Table ([item] varChar(8000)) As 
Begin 

Declare @item VarChar(8000); 

while charIndex(@delimit, @input, 0) <> 0 Begin 

    Select 
     @item = rTrim(lTrim(subString(@input, 1, charIndex(@delimit, @input, 0) - 1))), 
     @input = rTrim(lTrim(subString(@input, charIndex(@delimit, @input, 0) + Len(@delimit), Len(@input)))); 

    If Len(@item) > 0 Insert Into @List Select @item 

End 

If Len(@input) > 0 Insert Into @List Select @input 

Return; 

End 

然后，你需要加入值回你的国家表，并重新加入他们的行列。这会让你大部分的方式：

Select ID 
     ,[Name] as [User] 
     ,(
     Select [country] + ', ' 
     From [Countries] 
     Where [ID] In (
      Select Cast([item] As Integer) 
      From dbo.split(U.Countries, ',') 
      Where IsNumeric(item) = 1) 
     Order By [country] 
     For XML Path('')) As [CountriesByName] 
From [Users] As U 

但是，这留下了一个尾随逗号。您可能需要删除一些其他层，但以防万一，你必须这样做在SQL，这应该工作：

Select ID 
     ,[User] 
     ,Left([CountriesByName], Len([CountriesByName]) - 1) As [CountriesByName] 
From (
    Select ID 
      ,[Name] as [User] 
      ,(
      Select [country] + ', ' 
      From [Countries] 
      Where [ID] In (
       Select Cast([item] As Integer) 
       From dbo.split(U.Countries, ',') 
       Where IsNumeric(item) = 1) 
      Order By [country] 
      For XML Path('')) As [CountriesByName] 
    From [Users] As U) As [Results] 

Answer 2

试试Common Table Expression查询。 Simple-Talk有一个很好的walkthrough，它解释了SQL接触的不同方法，并给出了使用CTE的例子（查找WITH语句）。

Answer 3

如果您标准化您的数据分成三个数据表，然后下面的作品，你要什么做。这是使用我自己的模式，因为我必须敲一些表来测试它）。

Select 
UserId, UserName, 
(
    Select 
     CountryName + ',' 
    From 
     Country As C 
    Inner Join 
     UserCountry As UC 
    On C.CountryId = UC.CountryId 
    Where 
     UC.UserId = [User].UserId 
    ORDER BY 
     CountryName 
    FOR XML PATH('') 
) As Countries 

从 [User];

Answer 4

首先，我将创建一个存储过程，该过程需要一串国家ID并使用动态SQL返回国家/地区名称列表。

create proc dbo.getCoutries(@ids nvarchar(200)) 
as 
begin 
declare @sql nvarchar(200) 
set @sql = 'select @countries = @countries + Country+ 
    '', '' from Countries where ID in ('+@ids+')' 
declare @countries nvarchar(200) 
set @countries = '' 
DECLARE @ParmDefinition nvarchar(500); 
SET @ParmDefinition = N'@countries nvarchar(200) OUTPUT'; 


EXECUTE sp_executesql @sql, 
    @ParmDefinition, 
    @countries=@countries OUTPUT; 

select substring(@countries,1,len(@countries)-1) Countries 

end 

go 

所以现在exec execCoutries'2,5'返回“德国，加拿大”。 一旦做到这一点，我们现在需要下面的代码运行 回报看起来像表：

Name  Countries 
User1 Australia, Germany, USA 
User2 Germany, Canada 



--The variable we will use to loop thru the user ids 
declare @userId int 
set @userId = 0 

-- hold the string of country ids 
declare @countryIds varchar(30) 

-- a temp table that we will populate 
-- it will have the users ID and then the 
-- string of countries (i.e "Germany, Canada") 
declare @results as 
table 
(userId int, 
countries varchar(200)) 


--Loop thru each row in the Users table. 
while 1=1 
begin 
select @userId=min(ID) 
from Users 
where ID > @userId 

if @userId is null 
    break 

--get the string of country ids for this user 
select @countryIds=Countries 
from Users 
where ID = @userId 

--use our stored proc to bring back the string of names 
insert into @results 
(countries) 
exec getCoutries @countryIds 

--update the userId for our new row 
update @results 
set UserId = @UserId 
where UserId is null 


end 

-- return the user and his list of countries 
select u.Name, r.Countries 
from Users u 
inner join @results r 
on u.ID = r.UserId 

GO