Question

I am getting strange results from a query using XML EXPLICIT mode in T-SQL (SQL Server 2008).

Can someone explain what I am doing wrong?

Here is my example:

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

and here is the strange result I am getting:

<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>

OK – I think I need to be more specific, and include the “Sequence” portion of my problem as well as the original issue. Given the following data set:

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);

How can I get the following result that has data like this:

<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>

with the

elements ordered by sequence and their child elements order by sequence within each?

Thanks for your help…I hope this more fully explains what I need, and why I am trying to use explicit mode.

Answer 1

With SQL Server 2005 and up, forget about FOR XML EXPLICIT – use FOR XML PATH instead – it’s much easier to use, more expressive, more intuitive.

Try this:

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')

Output will be this: (order by p.sequence on the outer scope, and c.sequence in the inner scope)

<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>

See the MSDN documentation on what’s new in SQL Server 2005 for more hints and tips how to use the FOR XML PATH to generate XML from your database contents…