从执行计划中分解XML

Question

我首先要说，我讨厌XML，这是一种可怕的东西，但有时却是必要的。

我目前的问题是，我正试图从执行计划(由用户提供，所以可以是任何大小)中获取XML，并将其分解到一个表中以供进一步操作。我现在只有两个选择;

1. 我可以计算出执行计划可用的最大节点数量(我怀疑这将是很多)，并创建可用于任何XML输入的整个脚本。这将是一次的事情，所以不是一个问题。
2. 另一种方法是动态计算节点数量，并根据要求创建输出。

过去有人做过类似的练习吗?我发现的所有示例查询都已经知道了输出字段。

Answer 1

一个非常直接的方法可能是这样的(而@x是您的xml执行计划):

DECLARE @x XML=
N'<root>
    <ElementE1 AttributA1="A1-text belongs to E1[1]" OneMore="xyz">E1-Text 2</ElementE1>
    <ElementE1 AttributA1="A1-text belongs to E1[2]">E1-Text 2</ElementE1>
    <ElementParent>
      <subElement test="sub"/>
      Free text
    </ElementParent>
  </root>';
DECLARE @idoc INT;
EXEC sp_xml_preparedocument @idoc OUTPUT, @x;   
SELECT * FROM OPENXML (@idoc, '*');   
EXEC sp_xml_removedocument @idoc;  

结果(不是所有列)

+----+----------+----------+--------------+------+--------------------------+
| id | parentid | nodetype | localname    | prev | text                     |
+----+----------+----------+--------------+------+--------------------------+
| 0  | NULL     | 1        | root         | NULL | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 2  | 0        | 1        | ElementE1    | NULL | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 3  | 2        | 2        | AttributA1   | NULL | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 13 | 3        | 3        | #text        | NULL | A1-text belongs to E1[1] |
+----+----------+----------+--------------+------+--------------------------+
| 4  | 2        | 2        | OneMore      | NULL | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 14 | 4        | 3        | #text        | NULL | xyz                      |
+----+----------+----------+--------------+------+--------------------------+
| 5  | 2        | 3        | #text        | NULL | E1-Text 2                |
+----+----------+----------+--------------+------+--------------------------+
| 6  | 0        | 1        | ElementE1    | 2    | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 7  | 6        | 2        | AttributA1   | NULL | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 15 | 7        | 3        | #text        | NULL | A1-text belongs to E1[2] |
+----+----------+----------+--------------+------+--------------------------+
| 8  | 6        | 3        | #text        | NULL | E1-Text 2                |
+----+----------+----------+--------------+------+--------------------------+
| 9  | 0        | 1        | ElementParent| 6    | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 10 | 9        | 1        | subElement   | NULL | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 11 | 10       | 2        | test         | NULL | NULL                     |
+----+----------+----------+--------------+------+--------------------------+
| 16 | 11       | 3        | #text        | NULL | sub                      |
+----+----------+----------+--------------+------+--------------------------+
| 12 | 9        | 3        | #text        | 10   | Free text                |
+----+----------+----------+--------------+------+--------------------------+

id清楚地表明，该算法是宽度优先，没有id=1(为什么)，nodetype允许区分元素，属性和(浮动)文本。prev列指向链中的兄弟节点。缺少的列与名称空间相关…

使用FROM OPENXML的方法已经过时了，但这是少数情况之一，它可能仍然非常有用…

你得到一个包含id和parentid的列表，你可以用递归CTE查询…

Answer 2

将XML分解为元素和属性及其路径和父元素的脚本。从http://beyondrelational.com/modules/2/blogs/28/posts/10495/xquery-lab-58-select-from-xml.aspx

CREATE FUNCTION [dbo].[XMLTable]( 
    @x XML 
) 
RETURNS TABLE 
AS RETURN 
/*---------------------------------------------------------------------- 
This INLINE TVF uses a recursive CTE that processes each element and 
attribute of the XML document passed in. 
----------------------------------------------------------------------*/ 
WITH cte AS ( 
    /*------------------------------------------------------------------ 
    Anchor part of the recursive query. Retrieves the root element 
    of the XML document 
    ------------------------------------------------------------------*/ 
    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 
    /*------------------------------------------------------------------ 
    Start recursion. Retrieve each child element of the parent node 
    ------------------------------------------------------------------*/ 
    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 
    /*------------------------------------------------------------------ 
    Attributes do not need recursive calls. So add the attributes 
    to the query output at the end. 
    ------------------------------------------------------------------*/ 
    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;
go
SELECT * FROM dbo.XMLTable(' 
<employees> 
    <emp name="jacob"/> 
    <emp name="steve"> 
        <phone>123</phone>
     some text                      
    </emp> 
</employees> 
')