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For XML Path,forxmlpath

For XML Path,forxmlpath


关于For XML Path的用法  创建的表数据如图:
先看下for xml path的初始用法:select ClassID,Sex,Age,Name from #PersonInfo for xml path('PersonInfo')   从名字就看可以看出用法,for xml  !!!
在使用过程中感觉通常是恶group by 一起用的。举例如下:
--统计每个班中超过22岁的男同学信息
select ClassID,COUNT(1) as '超过22岁个数',
(select Name+',' from #PersonInfo where ClassID=p.ClassID for xml path ('')) as '姓名集合'
from #PersonInfo p where Sex='男' and Age>22 group by ClassID order by ClassID
select ClassID,Age,COUNT(1) as '超过22岁个数',
(select Name+',' from #PersonInfo where ClassID=p.ClassID and Age=p.Age for xml path ('')) as '姓名集合'
from #PersonInfo p where Sex='男' and Age>22 group by ClassID,Age order by ClassID
select ClassID,Age,COUNT(1) as '超过22岁个数',
(select Name+',' from #PersonInfo where ClassID=p.ClassID and Age=p.Age for xml path ('')) as '姓名集合'
from #PersonInfo p where Sex='男' group by ClassID,Age having Age>22 order by ClassID

结果如下:
感觉having的用处没有想象中那么大。只有在group by后使用,并且是聚合函数是用处才大,不然直接写在where后面即可。 补充一下:姓名集合最后面的逗号可以通过stuff函数去除掉。

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