generate structured (xml) document from hierarchical table data (T-SQL)

Question

I have a table like this (simplified):

ID   |   Name  |   Parent
---------------------------------
1    |  IND    |   NULL
2    |  INS    |   5
3    |  CON           


        

Answer 1

You can also do this without creating a separate function, by including the sub-query as an additional column that returns XML. For example, the following will return a hierarchical XML document containing users and their associated list of roles:

SELECT 
    FirstName, LastName,
    CONVERT(XML, 
      (SELECT r.UserID, r.RoleID
       FROM global.[UserRole] r
       WHERE r.USerID = [user].UserID
       FOR XML RAW ('Role'), ELEMENTS, root('Roles')
      ))
FROM global.[user]
FOR XML RAW ('User'), ELEMENTS, root('Users')

Answer 2

Based on Recep's answer (see comments) I created the following solution for this problem:

1. Create a recursive function

CREATE function SelectChild(@key as int)
returns xml
begin
    return (
        select 
            IdIndustry as "@key", 
            ParentId as "@parentkey",
            IndustryCode as "@Code",
            IndustryName as "@Name",
            dbo.SelectChild(IdIndustry)
        from tblIndustryCodes
        where ParentId = @key
        for xml path('record'), type
    )
end

2. Build a SELECT statement, that calls the function

SELECT 
    IdIndustry AS "@key", 
    '' AS "@parentkey",
    IndustryCode as "@Code",
    IndustryName as "@Name",
    dbo.SelectChild(IdIndustry)     
FROM dbo.tblIndustryCodes
WHERE ParentId is null
FOR XML PATH ('record')

This creates a hierarchical XML, no matter how deep the tree actually is:

<record key="1" parentkey="" Code="IND" Name="Industry">
  <record key="2" parentkey="1" Code="AUTO" Name="Automotive" />
  <record key="3" parentkey="1" Code="PHARM" Name="Pharmaceuticals" />
</record>
<record key="4" parentkey="" Code="FIN" Name="Finance">
  <record key="5" parentkey="4" Code="CFIN" Name="Corporate Finance">
    <record key="6" parentkey="5" Code="CMRKT" Name="Capital Markets" />
  </record>
</record>
<record key="7" parentkey="" Code="CON" Name="Cosulting">
  <record key="8" parentkey="7" Code="IMPL" Name="Implementation" />
  <record key="9" parentkey="7" Code="STRAT" Name="Strategy" />
</record>