Loop for extracting attributes of elements XML

Question

I need to extract all attributes from a long list of various elements. Therefore, I'm seeking to build a loop going through all of my elements and return their attributes.

Through several posts I have been able to write the code below. However, I have more than a 1000 elements why I would extremely glad if it somehow is possible to build a loop around the latter part rather than copying it for all elements.

with cte as
(
select cast(
'<schema fwRel="2"> 
<taxFormId isPrimeKey="true" fkRef="C1-TXFRM" mapField="TAX_FORM_ID" dataType="string"/>  
<formType fkRef="C1-FRMTY" mapField="FORM_TYPE_CD" dataType="string"/>  
<bo suppress="true" required="true" fkRef="F1-BUSOB" mapField="BUS_OBJ_CD" dataType="string"/>
<transferReason mdField="C1_TXF_TFRRSN_FLG" dataType="lookup" mapXML="BO_DATA_AREA" lookup="C1_TXF_TFRRSN_FLG"/>  
</schema>' as xml) xml_col
)

select cte.xml_col.value('(/schema/taxFormId/@fkRef)[1]', 'varchar(100)') as Dummy1
cte.xml_col.value('(/schema/taxFormId/@mapField)[1]', 'varchar(100)') as Dummy2
cte.xml_col.value('(/schema/taxFormId/@dataType)[1]', 'varchar(100)') as Dummy3
cte.xml_col.value('(/schema/taxFormId/@mapXML)[1]', 'varchar(100)') as Dummy4

from cte

I hope I have provided enough information

You mentioned the code - can you add it? – Damian Jan 10 '17 at 19:49 — Damian, Jan 10 '17 at 19:49
Somehow Edge screwed me. It's attached now – D. Daugs Jan 10 '17 at 19:55 — D. Daugs, Jan 10 '17 at 19:55

score 1 · Accepted Answer · answered Jan 10 '17 at 22:35

An easy way to get attributes listed:

with cte as
(
select cast(
'<schema fwRel="2">
  <taxFormId isPrimeKey="true" fkRef="C1-TXFRM" mapField="TAX_FORM_ID" dataType="string" />
  <formType fkRef="C1-FRMTY" mapField="FORM_TYPE_CD" dataType="string" />
  <bo suppress="true" required="true" fkRef="F1-BUSOB" mapField="BUS_OBJ_CD" dataType="string" />
  <transferReason mdField="C1_TXF_TFRRSN_FLG" dataType="lookup" mapXML="BO_DATA_AREA" lookup="C1_TXF_TFRRSN_FLG" />
</schema>' as xml) xml_col
)

--The query uses .nodes(N'/schema/*') to list all nodes below <schema> and .nodes(N'@*') to list all attributes within this node:

select nd.value(N'local-name(.)',N'nvarchar(max)') AS NodeName
      ,attr.value(N'local-name(.)',N'nvarchar(max)') AS AttrName
      ,attr.value(N'.',N'nvarchar(max)') AS AttrValue
from cte
OUTER APPLY xml_col.nodes(N'/schema/*') AS A(nd)
OUTER APPLY A.nd.nodes(N'@*') AS B(attr)

The result:

taxFormId       isPrimeKey  true
taxFormId       fkRef       C1-TXFRM
taxFormId       mapField    TAX_FORM_ID
taxFormId       dataType    string
formType        fkRef       C1-FRMTY
formType        mapField    FORM_TYPE_CD
formType        dataType    string
bo              suppress    true
bo              required    true
bo              fkRef       F1-BUSOB
bo              mapField    BUS_OBJ_CD
bo              dataType    string
transferReason  mdField     C1_TXF_TFRRSN_FLG
transferReason  dataType    lookup
transferReason  mapXML      BO_DATA_AREA
transferReason  lookup      C1_TXF_TFRRSN_FLG

If you need a statement like the one in your example one could create it dynamically (as string) and use EXEC to execute this (dynamic SQL).

score 0 · Answer 2 · answered Jan 10 '17 at 20:03

It may be a little over-kill, but I often use a TVF to parse and hash large XML files. The function will return the data in a parent/child hierarchy structure with range keys R1/R2.

For example:

Declare @XML xml='
<schema fwRel="2"> 
    <taxFormId isPrimeKey="true" fkRef="C1-TXFRM" mapField="TAX_FORM_ID" dataType="string"/>  
    <formType fkRef="C1-FRMTY" mapField="FORM_TYPE_CD" dataType="string"/>  
    <bo suppress="true" required="true" fkRef="F1-BUSOB" mapField="BUS_OBJ_CD" dataType="string"/>
    <transferReason mdField="C1_TXF_TFRRSN_FLG" dataType="lookup" mapXML="BO_DATA_AREA" lookup="C1_TXF_TFRRSN_FLG"/>
</schema>'

Select * from [dbo].[udf-XML-Hier](@XML) Order by R1

Returns

You'll notice there are columns for Element Name, Attribute Name, XPath, Title (optional), and Value. The R1,R2,Lvl,ID and PT are all derived.

Being a TVF, you could apply any WHERE or ORDER desired

The UDF (with original source) if interested

CREATE FUNCTION [dbo].[udf-XML-Hier](@XML xml)

Returns Table 
As Return

with  cte0 as ( 
                  Select Lvl       = 1
                        ,ID        = Cast(1 as int) 
                        ,Pt        = Cast(NULL as int)
                        ,Element   = x.value('local-name(.)','varchar(150)')
                        ,Attribute = cast('' as varchar(150))
                        ,Value     = x.value('text()[1]','varchar(max)')
                        ,XPath     = cast(concat(x.value('local-name(.)','varchar(max)'),'[' ,cast(Row_Number() Over(Order By (Select 1)) as int),']') as varchar(max))
                        ,Seq       = cast(10000001 as varchar(max))
                        ,AttData   = x.query('.') 
                        ,XMLData   = x.query('*') 
                  From   @XML.nodes('/*') a(x) 
                  Union  All
                  Select Lvl       = p.Lvl + 1 
                        ,ID        = Cast( (Lvl + 1) * 1024 + (Row_Number() Over(Order By (Select 1)) * 2) as int ) * 10
                        ,Pt        = p.ID
                        ,Element   = c.value('local-name(.)','varchar(150)')
                        ,Attribute = cast('' as varchar(150))
                        ,Value     = cast( c.value('text()[1]','varchar(max)') as varchar(max) ) 
                        ,XPath     = cast(concat(p.XPath,'/',c.value('local-name(.)','varchar(max)'),'[',cast(Row_Number() Over(PARTITION BY c.value('local-name(.)','varchar(max)') Order By (Select 1)) as int),']') as varchar(max) )
                        ,Seq       = cast(concat(p.Seq,' ',10000000+Cast( (Lvl + 1) * 1024 + (Row_Number() Over(Order By (Select 1)) * 2) as int ) * 10) as varchar(max))
                        ,AttData   = c.query('.') 
                        ,XMLData   = c.query('*') 
                  From   cte0 p 
                  Cross  Apply p.XMLData.nodes('*') b(c) 
              )
    , cte1 as (   
                  Select R1 = Row_Number() over (Order By Seq),A.*
                  From  (
                          Select  Lvl,ID,Pt,Element,Attribute,Value,XPath,Seq From cte0
                          Union All
                          Select Lvl       = p.Lvl+1
                                ,ID        = p.ID + Row_Number() over (Order By (Select NULL)) 
                                ,Pt        = p.ID
                                ,Element   = p.Element
                                ,Attribute = x.value('local-name(.)','varchar(150)')
                                ,Value     = x.value('.','varchar(max)')
                                ,XPath     = p.XPath + '/@' + x.value('local-name(.)','varchar(max)')
                                ,Seq       = cast(concat(p.Seq,' ',10000000+p.ID + Row_Number() over (Order By (Select NULL)) ) as varchar(max))
                          From   cte0 p 
                          Cross  Apply AttData.nodes('/*/@*') a(x) 
                        ) A 
               )

Select A.R1
      ,R2  = IsNull((Select max(R1) From cte1 Where Seq Like A.Seq+'%'),A.R1)
      ,A.Lvl
      ,A.ID
      ,A.Pt
      ,A.Element
      ,A.Attribute
      ,A.XPath
      ,Title = Replicate('|---',Lvl-1)+Element+IIF(Attribute='','','@'+Attribute)
      ,A.Value
 From  cte1 A

/*
Source: http://beyondrelational.com/modules/2/blogs/28/posts/10495/xquery-lab-58-select-from-xml.aspx

Declare @XML xml='<person><firstname preferred="Annie" nickname="BeBe">Annabelle</firstname><lastname>Smith</lastname></person>'
Select * from [dbo].[udf-XML-Hier](@XML) Order by R1
*/

Thanks! :) I managed to get this working as well. However, as you stated yourself it is a minor overkill. — D. Daugs, Jan 11 '17 at 08:48

Loop for extracting attributes of elements XML

2 Answers2