T-SQL：交叉应用；行项目上的迭代次数过多

在分解了一些重要的Xml之后，我几乎得到了想要的结果——但是在查看结果之后，我发现在解析的一个部分中，我无法轻松解决迭代每个副标题的所有行详细信息的模式——因此，与其为所有行项目总共写出3条记录，我为每个sub写了三行项目——假设我有两行。我总共得到了6分-（在下面的代码中，我将该模式提炼为通用标题/副标题/细节关系模型

    DECLARE @MetroXML xml
    SET @MetroXML =
    '<Header>
       <col1>Conoco</col1>
       <col2>ORD-1111</col2>
       <SubHeaders>
         <SubHeader>
          <col1>Dallas</col1>
          <col2>BOL-2213</col2>
         <Details>
          <Detail>
            <col1>Diesel</col1>
            <col2>7600.00</col2>
          </Detail>
         </Details>
        </SubHeader>
        </SubHeaders>
        <SubHeaders>
         <SubHeader>
          <col1>Fort Worth</col1>
          <col2>BOL-2216</col2>
         <Details>
          <Detail>
            <col1>Ethanol</col1>
            <col2>1852.00</col2>
          </Detail>
          <Detail>
            <col1>Unleaded</col1>
            <col2>900.00</col2>
          </Detail>
         </Details>
       </SubHeader>
      </SubHeaders>
     </Header>';


    INSERT INTO [scratch].GenericHeader
     SELECT T.c.value('col1[1]','varchar(10)') AS 'col1',
            T.c.value('col2[1]','varchar(10)') AS 'col2'
       FROM @MetroXML.nodes('/Header') T(c);


    INSERT [scratch].GenericSubHeader
     (id,col1,col2)
    SELECT 
      h.id,
      n.x.value('col1[1]','varchar(10)') AS 'col1',
      n.x.value('col2[1]','varchar(10)') AS 'col2'
     FROM [scratch].GenericHeader h
      CROSS APPLY @MetroXML.nodes('/Header/SubHeaders/SubHeader') n(x);


     INSERT [scratch].GenericDetail
     (id,subid,col1,col2)
      SELECT 
       s.id,
       s.subid,
       n.x.value('col1[1]','varchar(10)') AS 'col1',
       n.x.value('col2[1]','varchar(10)') AS 'col2'
     FROM [scratch].GenericSubHeader s
      CROSS APPLY @MetroXML.nodes('/Header/SubHeaders/SubHeader/Details/Detail') as n(x);


     select * from [scratch].GenericHeader
      where id = 24;

     select * from [scratch].GenericSubHeader
      where id = 24;

     select * from [scratch].GenericDetail
      where id = 24;

我想要的是：

id|subid|detid|col1     |col2
--------------------------------
24|44   |22   |Diesel   |7600.00
24|48   |23   |Ethanol  |1852.00
24|48   |24   |Unleaded |900.00

---

获得重复行的原因是对

GenericSubHeader

中每行的整个XML使用交叉应用。您必须找到一种方法，将

GenericSubHeader

中生成的

ID

和

GenericSubHeader

中生成的

subid

映射到XML的相关部分

如果您使用的是SQL Server 2008或更高版本，则可以创建一个表变量，该变量保存生成的id和所属的xml子节点

declare @GH table
(
  id int,
  sub xml
);

merge scratch.GenericHeader as T
using 
  (
    select T.c.value('col1[1]','varchar(10)'),
           T.c.value('col2[1]','varchar(10)'),
           T.c.query('SubHeaders')
    from @MetroXML.nodes('/Header') T(c)
  ) as S(col1, col2, sub)
on 0 = 1
when not matched then
  insert (col1, col2) values(S.col1, S.col2)
output inserted.id, S.sub into @GH;  

declare @GSH table
(
  id int,
  subid int,
  det xml
);

merge scratch.GenericSubHeader as T
using
  (
    select h.id,
           n.x.value('col1[1]','varchar(10)'),
           n.x.value('col2[1]','varchar(10)'),
           n.x.query('Details')
    from @GH as h
      cross apply h.sub.nodes('/SubHeaders/SubHeader') n(x)
  ) as S(id, col1, col2, det)
on 0 = 1
when not matched then
  insert (id, col1, col2) values (S.id, S.col1, S.col2)
output inserted.id, inserted.subid, S.det into @GSH;

insert into scratch.GenericDetail(id, subid, col1, col2)
select s.id,
       s.subid,
       n.x.value('col1[1]','varchar(10)') AS 'col1',
       n.x.value('col2[1]','varchar(10)') AS 'col2'
from @GSH as s
  cross apply s.det.nodes('/Details/Detail') as n(x);

---

把你得到的放在问题中，而不是评论中谢谢！谢谢！谢谢！最后一个结合tsql的算法不仅有效，而且高效、清晰、实用！

declare @GH table
(
  id int,
  sub xml
);

merge scratch.GenericHeader as T
using 
  (
    select T.c.value('col1[1]','varchar(10)'),
           T.c.value('col2[1]','varchar(10)'),
           T.c.query('SubHeaders')
    from @MetroXML.nodes('/Header') T(c)
  ) as S(col1, col2, sub)
on 0 = 1
when not matched then
  insert (col1, col2) values(S.col1, S.col2)
output inserted.id, S.sub into @GH;  

declare @GSH table
(
  id int,
  subid int,
  det xml
);

merge scratch.GenericSubHeader as T
using
  (
    select h.id,
           n.x.value('col1[1]','varchar(10)'),
           n.x.value('col2[1]','varchar(10)'),
           n.x.query('Details')
    from @GH as h
      cross apply h.sub.nodes('/SubHeaders/SubHeader') n(x)
  ) as S(id, col1, col2, det)
on 0 = 1
when not matched then
  insert (id, col1, col2) values (S.id, S.col1, S.col2)
output inserted.id, inserted.subid, S.det into @GSH;

insert into scratch.GenericDetail(id, subid, col1, col2)
select s.id,
       s.subid,
       n.x.value('col1[1]','varchar(10)') AS 'col1',
       n.x.value('col2[1]','varchar(10)') AS 'col2'
from @GSH as s
  cross apply s.det.nodes('/Details/Detail') as n(x);