一列多行值合并成一个值(MS SQL SERVER 2008)

现在有两张表，一张手机型号表(PhoneModel),一张手机制造商表(PhoneCompany)

PhoneModel表结构如下:





PhoneCompany表结构如下:





,PhoneModel表通过字段coid与PhoneCompany表的coid相关联.现在的需求是如下图":





新增一列查询models,这列显示一个手机制造商所生产的所有手机型号。因为一个手机制造商会生产很多型号的手机，就需要把多条手机型号的记录合并成一个值.

使用for xml path可以实现类似的需求。

SELECT coid,company,(SELECT model+',' FROM dbo.PhoneModel WHERE coid=pc.coid FOR XML PATH('')) AS  models FROM dbo.PhoneCompany AS pc

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

于是写出了上述SQL句,查询结果如下:



,

最后一个型号总是有逗号(如下图)





于是改进之，把最后一个逗号去掉

SELECT coid,company,LEFT(models,LEN(models)-1) AS models FROM

(

SELECT coid,company,(SELECT model+',' FROM dbo.PhoneModel WHERE coid=pc.coid FOR XML PATH('')) AS  models FROM dbo.PhoneCompany AS pc

)

AS p

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

查询结果如下









于是把最后一个逗号都去掉了.

但是一个诡异的问题出现了，通过asp程序读取models这列的值会读取不到值，查询分析器里运行是有值的，急中生智再做一次变换

SELECT coid,company,LEFT(models,LEN(models)-1) AS models FROM

(

SELECT coid,company,convert(VARCHAR(5000),(SELECT model+',' FROM dbo.PhoneModel WHERE coid=pc.coid FOR XML PATH(''))) AS  models FROM dbo.PhoneCompany AS pc

)

AS p

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

问题是解决了，可是具体原因还是不太明白，为什么asp程序会读取不到值？