SQL XML Problemas explícitos con la creación de árbol XML (padre-hijo)

Question

Estoy enfrentando algunos problemas con XML explícito en SQL Server, donde no emite XML de acuerdo con la relación que especifiqué en SQL Query.La consulta se realiza en la base de datos de pubs y, aunque la ruta XML es más fácil de usar, la necesidad de mi entrenador, se realiza en XML explícita.

    SELECT  1               AS Tag,
        NULL            AS Parent,
        NULL            AS [TitleTypes!1],
        NULL            AS [TitleType!2!Type],
        NULL            AS [TitleType!2!AveragePrice],
        NULL            AS [Title!3!title_id],
        NULL            AS [Title!3!price]

UNION ALL
SELECT  2,
        1,
        NULL            ,
        type            AS [TitleType!2!Type],
        AVG(price)      AS [TitleType!2!AveragePrice],
        NULL            AS [Title!3!title_id],
        NULL            AS [Title!3!price]
from titles 
GROUP BY type   
UNION ALL
SELECT  3,
        2,
        NULL            ,
        type            AS [TitleType!2!Type],
        NULL            AS [TitleType!2!AveragePrice],
        title_id        AS [Title!3!title_id],
        price           AS [Title!3!price]

from titles     

FOR XML EXPLICIT;

La salida que produce:

    <TitleTypes>
  <TitleType Type="business    " AveragePrice="13.7300" />
  <TitleType Type="mod_cook    " AveragePrice="11.4900" />
  <TitleType Type="popular_comp" AveragePrice="21.4750" />
  <TitleType Type="psychology  " AveragePrice="13.5040" />
  <TitleType Type="trad_cook   " AveragePrice="15.9633" />
  <TitleType Type="UNDECIDED   ">
    <Title title_id="BU1032" price="19.9900" />
    <Title title_id="BU1111" price="11.9500" />
    <Title title_id="BU2075" price="2.9900" />
    <Title title_id="BU7832" price="19.9900" />
    <Title title_id="MC2222" price="19.9900" />
    <Title title_id="MC3021" price="2.9900" />
    <Title title_id="MC3026" />
    <Title title_id="PC1035" price="22.9500" />
    <Title title_id="PC8888" price="20.0000" />
    <Title title_id="PC9999" />
    <Title title_id="PS1372" price="21.5900" />
    <Title title_id="PS2091" price="10.9500" />
    <Title title_id="PS2106" price="7.0000" />
    <Title title_id="PS3333" price="19.9900" />
    <Title title_id="PS7777" price="7.9900" />
    <Title title_id="TC3218" price="20.9500" />
    <Title title_id="TC4203" price="11.9500" />
    <Title title_id="TC7777" price="14.9900" />
  </TitleType>
</TitleTypes>

La salida que quiero:

   <TitleTypes>
    <TitleType Type="business" AveragePrice="11.22">
        <Title title_id="BU1111" Price="11.34"/>
        <Title title_id="TC7777" Price="14.2"/>
    </TitleType>
    <TitleType Type="popular_comp" AveragePrice="13.99">
        <Title title_id="BU1111" Price="15.9"/>
        <Title title_id="TC7777" Price="16.22"/>
    </TitleType>
</TitleTypes>

Answer 1

Por lo general, no necesita un modo explícito en absoluto.Puedes generar casi todos los XML. Quiero con para la ruta XML :

select
    t1.type as [@Type],
    avg(t1.price) as [@AveragePrice],
    (
        select
            t2.title_id as [@title_id],
            t2.price as [@price]
        from titles as t2
        where t2.type = t1.type
        for xml path('Title'), type
    )
from titles as t1
group by t1.type
for xml path('TitleType'), root('TitleTypes')

Pero dado que su XML es un atributo centrado, es aún más fácil para usted usar >>para XML RAW :

select
    t1.type as [Type],
    avg(t1.price) as AveragePrice,
    (
        select
            t2.title_id
            t2.price
        from titles as t2
        where t2.type = t1.type
        for xml raw('Title'), type
    )
from titles as t1
group by t1.type
for xml raw('TitleType')

Demo de violín SQL

Answer 2

Aquí está la solución que funcionó para mí.Mira en el orden por la cláusula.Si está utilizando SQL Server Management Studio en orden por cláusula, le mostrará un posible nombre de columna por el cual puede formatear su salida XML como desee.

SELECT  1               AS Tag,
            NULL            AS Parent,
            NULL            AS [TitleTypes!1],
            NULL            AS [TitleType!2!Type],
            NULL            AS [TitleType!2!AveragePrice],
            NULL            AS [Title!3!title_id],
            NULL            AS [Title!3!price]

    UNION ALL
    SELECT  2,
            1,
            NULL            ,
            type            AS [TitleType!2!Type],
            AVG(price)      AS [TitleType!2!AveragePrice],
            NULL            AS [Title!3!title_id],
            NULL            AS [Title!3!price]
    from titles 
    GROUP BY type   
    UNION ALL
    SELECT  3,
            2,
            NULL            ,
            type            AS [TitleType!2!Type],
            NULL            AS [TitleType!2!AveragePrice],
            title_id        AS [Title!3!title_id],
            price           AS [Title!3!price]

    from titles     

    ORDER BY [TitleTypes!1], [TitleType!2!Type], [Title!3!title_id] ,Tag

    FOR XML EXPLICIT;

P.s.Para XML explícito succiona.Pero si está desarrollando / actualizando un sistema realmente antiguo, debe conocerlo antes de reemplazar con técnicas más nuevas.