我在T-SQL（SQL Server 2008）中使用XML EXPLICIT无法获得正确的结果

Question

我在T-SQL（SQL Server 2008）中使用XML EXPLICIT模式从查询中得到奇怪的结果。

有人可以解释我在做什么错吗？

这是我的示例：

declare @parents table(id int, connection int, title nvarchar(255));
declare @children table(id int, connection int, title nvarchar(255));

insert into @parents(id, connection, title)
values(1, 21, '1');
insert into @parents(id, connection, title)
values(2, 22, '2');
insert into @parents(id, connection, title)
values(3, 23, '3');
insert into @parents(id, connection, title)
values(4, 24, '4');
insert into @parents(id, connection, title)
values(5, 25, '5');
insert into @parents(id, connection, title)
values(6, 26, '6');

insert into @children(id, connection, title)
values(1, 21, '1a');
insert into @children(id, connection, title)
values(2, 22, '2a');
insert into @children(id, connection, title)
values(3, 23, '3a');
insert into @children(id, connection, title)
values(4, 24, '4a');
insert into @children(id, connection, title)
values(5, 25, '5a');
insert into @children(id, connection, title)
values(6, 26, '6a');
insert into @children(id, connection, title)
values(7, 21, '1b');
insert into @children(id, connection, title)
values(8, 22, '2b');
insert into @children(id, connection, title)
values(9, 23, '3b');
insert into @children(id, connection, title)
values(10, 24, '4b');
insert into @children(id, connection, title)
values(11, 25, '5b');
insert into @children(id, connection, title)
values(12, 26, '6b');

select 1 as tag, null as parent,
 id as [p!1!id],
 title as [p!1!title],
 null as [c!2!id],
 null as [c!2!title]
from @parents p
union
 select 2 as tag, 1 as parent,
 p.id, 
 p.title, 
 c.id,
 c.title
from @parents p, @children c
where p.connection = c.connection
for xml explicit

这是我得到的奇怪结果：

<p id="1" title="1" />
<p id="2" title="2" />
<p id="3" title="3" />
<p id="4" title="4" />
<p id="5" title="5" />
<p id="6" title="6">
  <c id="1" title="1a" />
  <c id="7" title="1b" />
  <c id="2" title="2a" />
  <c id="8" title="2b" />
  <c id="3" title="3a" />
  <c id="9" title="3b" />
  <c id="4" title="4a" />
  <c id="10" title="4b" />
  <c id="5" title="5a" />
  <c id="11" title="5b" />
  <c id="6" title="6a" />
  <c id="12" title="6b" />
</p>

好的-我想我需要更加具体，并包括问题的“序列”部分以及原始问题。 给定以下数据集：

declare @parents table(id int, connection int, title nvarchar(255), sequence int);
declare @children table(id int, connection int, title nvarchar(255), sequence int);

insert into @parents(id, connection, title, sequence)
values(1, 21, '1', 6), (2, 22, '2', 2), (3, 23, '3', 4), (4, 24, '4', 3), (5, 25, '5', 5), (6, 26, '6', 1);

insert into @children(id, connection, title, sequence)
values(1, 21, '1a', 2), (2, 22, '2a', 2), (3, 23, '3a', 2), (4, 24, '4a', 1), (5, 25, '5a', 2), (6, 26, '6a', 1), (7, 21, '1b', 1), (8, 22, '2b', 1), (9, 23, '3b', 1), (10, 24, '4b', 2), (11, 25, '5b', 1), (12, 26, '6b', 2);

如何获得具有如下数据的以下结果：

<p id="6" title="6" sequence="1">
  <c id="6" title="6a" />
  <c id="12" title="6b" />
</p>
<p id="1" title="2" sequence="2">
 <c id="8" title="2b" sequence="1" />
 <c id="2" title="2a" sequence="2" />
</p>

与

每个元素内按顺序排序的元素及其子元素按顺序排序？

感谢您的帮助...我希望本文能更全面地说明我的需求以及为什么要尝试使用显式模式。

Answer 1

在SQL Server 2005及更高版本中，不必担心FOR XML EXPLICIT ，而应使用FOR XML PATH ，它更易于使用，更具表现力，更直观。

尝试这个：

SELECT
    p.ID AS '@id',
    p.title AS '@title',
    p.sequence as '@sequence',
    (SELECT 
         c.ID AS '@id', 
         c.Title AS '@title',
         c.sequence as '@sequence'
     FROM @children c 
     WHERE p.connection = c.connection
     ORDER BY c.sequence
     FOR XML PATH('c'), TYPE
    )
FROM    
    @parents p
ORDER BY    
    p.sequence
FOR XML PATH('p')

输出将是这样的：（在外部示波器上按p.sequence排序，在内部示波器上按c.sequence排序）

<p id="6" title="6" sequence="1">
  <c id="6" title="6a" sequence="1" />
  <c id="12" title="6b" sequence="2" />
</p>
<p id="2" title="2" sequence="2">
  <c id="8" title="2b" sequence="1" />
  <c id="2" title="2a" sequence="2" />
</p>
<p id="4" title="4" sequence="3">
  <c id="4" title="4a" sequence="1" />
  <c id="10" title="4b" sequence="2" />
</p>
<p id="3" title="3" sequence="4">
  <c id="9" title="3b" sequence="1" />
  <c id="3" title="3a" sequence="2" />
</p>
<p id="5" title="5" sequence="5">
  <c id="11" title="5b" sequence="1" />
  <c id="5" title="5a" sequence="2" />
</p>
<p id="1" title="1" sequence="6">
  <c id="7" title="1b" sequence="1" />
  <c id="1" title="1a" sequence="2" />
</p>

有关如何使用FOR XML PATH从数据库内容生成XML的更多提示和技巧，请参阅有关SQL Server 2005新增功能的MSDN文档 。

Answer 2

尝试这个。 给定此数据：

declare @parents table(id int, connection int, title nvarchar(255), sequence int);
declare @children table(id int, connection int, title nvarchar(255), sequence int);

insert into @parents(id, connection, title, sequence)
values(1, 21, '1', 6), (2, 22, '2', 2), (3, 23, '3', 4), (4, 24, '4', 3), (5, 25, '5', 5), (6, 26, '6', 1);

insert into @children(id, connection, title, sequence)
values(1, 21, '1a', 2), (2, 22, '2a', 2), (3, 23, '3a', 2), (4, 24, '4a', 1), (5, 25, '5a', 2), (6, 26, '6a', 1), (7, 21, '1b', 1), (8, 22, '2b', 1), (9, 23, '3b', 1), (10, 24, '4b', 2), (11, 25, '5b', 1), (12, 26, '6b', 2);

您是否要像这样选择陈述：

select p.id [@id], p.title [@title], p.sequence [@sequence], 
    (select c.id [@id], c.title [@title], c.sequence [@sequence]
     from @children c
     where c.connection = p.connection
     order by c.sequence
     for xml path('child'), type)
from @parents p
for xml path('parent'), type