¿Cómo puedo obtener una lista de nombres de elementos de un valor XML en SQL Server?

Question

Tengo una tabla con una columna XML en SQL Server 2k8. El siguiente código SQL recupera algo de XML:

SELECT TOP 1 my_xml_column FROM my_table 

Digamos que me devuelve el siguiente código XML

<a> 
    <b /> 
    <c> 
    <d /> 
    <d /> 
    <d /> 
    </c> 
</a> 

Lo que me gustaría conseguir es

/a 
/a/b 
/a/c 
/a/c/d 
/a/e 

En otras palabras, ¿cómo puedo obtener SQL Server para que me diga la estructura de mi XML?

que pueda hacer lo siguiente para obtener todos los nombres de los elemtns individuales:

SELECT C1.query('fn:local-name(.)') 
FROM my_table 
CROSS APPLY my_xml_column.nodes('//*') AS T (C1) 

Tal vez si había un equivalente a "local-name()" que devuelve la ruta completa del elemento que lo haría ¿Haz el truco?

Answer 1

Usted puede hacer esto sin problemas con XQuery y una CTE recursiva (sin OPENXML):

DECLARE @xml xml 
SET @xml = '<a><b /><c><d /><d /><d /></c></a>'; 

WITH Xml_CTE AS 
(
    SELECT 
     CAST('/' + node.value('fn:local-name(.)', 
      'varchar(100)') AS varchar(100)) AS name, 
     node.query('*') AS children 
    FROM @xml.nodes('/*') AS roots(node) 

    UNION ALL 

    SELECT 
     CAST(x.name + '/' + 
      node.value('fn:local-name(.)', 'varchar(100)') AS varchar(100)), 
     node.query('*') AS children 
    FROM Xml_CTE x 
    CROSS APPLY x.children.nodes('*') AS child(node) 
) 
SELECT DISTINCT name 
FROM Xml_CTE 
OPTION (MAXRECURSION 1000) 

realmente no está haciendo mucha magia XQuery, pero al menos está todo en línea, no requiere procedimientos almacenados, permisos especiales, etc.

Answer 2

sospecho que la implementación de XQuery de SQL Server no es hasta esta tarea, pero esta es otra manera de hacerlo (inspirado por this, adaptar según sea necesario):

DECLARE @idoc INT, @xml XML 
SET @xml = (SELECT TOP 1 my_xml_column FROM my_table) 
EXEC sp_xml_preparedocument @idoc OUTPUT, @xml; 

WITH 
    E AS (SELECT * FROM OPENXML(@idoc,'/',3)), 
    P AS 
    (
    -- anchor member 
    SELECT id, parentid, localname AS [Path] 
    FROM E WHERE parentid IS NULL 
    UNION ALL 
    -- recursive member 
    SELECT E.id, E.parentid, P.[Path] + '/' + localname AS [Path] 
    FROM P INNER JOIN E ON E.parentid = P.id 
    ) 
SELECT [Path] FROM P 

EXEC sp_xml_removedocument @idoc 

Answer 3

UDF para usted .....

SET ANSI_NULLS ON 
GO 
SET QUOTED_IDENTIFIER ON 
GO 
CREATE FUNCTION [dbo].[XMLTable](@x XML) 
RETURNS TABLE 
AS RETURN 
WITH cte AS ( 
SELECT 
     1 AS lvl, 
     x.value('local-name(.)','NVARCHAR(MAX)') AS Name, 
     CAST(NULL AS NVARCHAR(MAX)) AS ParentName, 
     CAST(1 AS INT) AS ParentPosition, 
     CAST(N'Element' AS NVARCHAR(20)) AS NodeType, 
     x.value('local-name(.)','NVARCHAR(MAX)') AS FullPath, 
     x.value('local-name(.)','NVARCHAR(MAX)') 
     + N'[' 
     + CAST(ROW_NUMBER() OVER(ORDER BY (SELECT 1)) AS NVARCHAR) 
     + N']' AS XPath, 
     ROW_NUMBER() OVER(ORDER BY (SELECT 1)) AS Position, 
     x.value('local-name(.)','NVARCHAR(MAX)') AS Tree, 
     x.value('text()[1]','NVARCHAR(MAX)') AS Value, 
     x.query('.') AS this,   
     x.query('*') AS t, 
     CAST(CAST(1 AS VARBINARY(4)) AS VARBINARY(MAX)) AS Sort, 
     CAST(1 AS INT) AS ID 
FROM @x.nodes('/*') a(x) 
UNION ALL 
SELECT 
     p.lvl + 1 AS lvl, 
     c.value('local-name(.)','NVARCHAR(MAX)') AS Name, 
     CAST(p.Name AS NVARCHAR(MAX)) AS ParentName, 
    CAST(p.Position AS INT) AS ParentPosition, 
     CAST(N'Element' AS NVARCHAR(20)) AS NodeType, 
     CAST(p.FullPath + N'/' + c.value('local-name(.)','NVARCHAR(MAX)') AS NVARCHAR(MAX)) AS FullPath, 
     CAST(p.XPath + N'/'+ c.value('local-name(.)','NVARCHAR(MAX)')+ N'['+ CAST(ROW_NUMBER() OVER(PARTITION BY c.value('local-name(.)','NVARCHAR(MAX)') 
     ORDER BY (SELECT 1)) AS NVARCHAR)+ N']' AS NVARCHAR(MAX)) AS XPath, 
     ROW_NUMBER() OVER(PARTITION BY c.value('local-name(.)','NVARCHAR(MAX)') 
     ORDER BY (SELECT 1)) AS Position, 
     CAST(SPACE(2 * p.lvl - 1) + N'|' + REPLICATE(N'-', 1) + c.value('local-name(.)','NVARCHAR(MAX)') AS NVARCHAR(MAX)) AS Tree, 
     CAST(c.value('text()[1]','NVARCHAR(MAX)') AS NVARCHAR(MAX)) AS Value, c.query('.') AS this, 
     c.query('*') AS t, 
     CAST(p.Sort + CAST((lvl + 1) * 1024 + (ROW_NUMBER() OVER(ORDER BY (SELECT 1)) * 2) AS VARBINARY(4)) AS VARBINARY(MAX)) AS Sort, 
     CAST((lvl + 1) * 1024 + (ROW_NUMBER() OVER(ORDER BY (SELECT 1)) * 2) AS INT) 
FROM cte p 
CROSS APPLY p.t.nodes('*') b(c)), cte2 AS ( 
              SELECT 
              lvl AS Depth, 
              Name AS NodeName, 
              ParentName, 
              ParentPosition, 
              NodeType, 
              FullPath, 
              XPath, 
              Position, 
              Tree AS TreeView, 
              Value, 
              this AS XMLData, 
              Sort, ID 
              FROM cte 
UNION ALL 
SELECT 
     p.lvl, 
     x.value('local-name(.)','NVARCHAR(MAX)'), 
     p.Name, 
     p.Position, 
     CAST(N'Attribute' AS NVARCHAR(20)), 
     p.FullPath + N'/@' + x.value('local-name(.)','NVARCHAR(MAX)'), 
     p.XPath + N'/@' + x.value('local-name(.)','NVARCHAR(MAX)'), 
     1, 
     SPACE(2 * p.lvl - 1) + N'|' + REPLICATE('-', 1) 
     + N'@' + x.value('local-name(.)','NVARCHAR(MAX)'), 
     x.value('.','NVARCHAR(MAX)'), 
     NULL, 
     p.Sort, 
     p.ID + 1 
FROM cte p 
CROSS APPLY this.nodes('/*/@*') a(x) 
) 
SELECT 
     ROW_NUMBER() OVER(ORDER BY Sort, ID) AS ID, 
     ParentName, ParentPosition,Depth, NodeName, Position, 
     NodeType, FullPath, XPath, TreeView, Value, XMLData 
FROM cte2