TSQL query for tree view control and remove empty elements from an xml file

问题

Query for treeview control, sometimes contains empty elements which throws an exception (when there are no attributes in an element) due to data-binding of the control the text values is set to "GrandChildOfFirstRow"

I did get rid of them in my query via xquery but is there an alternative way to doing this or a better smarter way to get rid of those empty elements, (I need the left outer join for proper records for this query) or is it possible to combine the xquery code into shorter code:

Query:

        declare @x as xml
     set @x =
    (
    SELECT distinct  
    Table1.AssetObjID, Table1.Asset_ID , Table1.FromLR, Table1.AssetType + ', ' + Table1.StreetName + ', ' +  Table1.FromMunicNo   as FirstRow,
    Table2.ACIObjID ,Table2.PAssetObjID, Table2.Feature_ID + ', ' + Table2.FeatureName   AS ChildOfFirstRow,
    Table3.ITMObjID  ,Table3.Item_ID + ',' + Table3.[DESC] as GrandChildOfFirstRow
    FROM  Table1 left outer join 
    Table2 ON Table1.AssetObjID = Table2.PAssetObjID left outer join 
    Table3 ON Table1.AssetObjID = Table3.AssetObjID AND Table2.ACIObjID = Table3.ACIObjID
    where Table1.AssetType ='xxxx' 

    for xml auto,root('xml')
    )    

--what it does is it only grabs one empty element and deletes only occurrences of that           

--specific element for the whole file 
--so If I have 2 or more elements which are empty in an xml file 
--I will have to repeat that code each time

    SET @x.modify('delete //*[not(node()) and not(./@*)]')
    SET @x.modify('delete //*[not(node()) and not(./@*)]')

回答1:

You can use for xml path() and build your nested levels with correlated sub-queries.

select Table1.AssetObjID as "@AssetObjID",
       Table1.Asset_ID as "@Asset_ID",
       Table1.FromLR as "@FromLR",
       Table1.AssetType + ', ' + Table1.StreetName + ', ' +  Table1.FromMunicNo   as "@FirstRow",
       (
       select Table2.ACIObjID as "@ACIObjID",
              Table2.PAssetObjID as "@PAssetObjID",
              Table2.Feature_ID + ', ' + Table2.FeatureName   AS "@ChildOfFirstRow",
              (
              select Table3.ITMObjID as "@ITMObjID",
                     Table3.Item_ID + ',' + Table3.[DESC] as "@GrandChildOfFirstRow"
              from Table3
              where Table1.AssetObjID = Table3.AssetObjID and 
                    Table2.ACIObjID = Table3.ACIObjID
              for xml path('Table3'), type
              )
       from Table2
       where Table1.AssetObjID = Table2.PAssetObjID
       for xml path('Table2'), type
       )
from Table1
where Table1.AssetType = 'xxxx'
for xml path('Table1'), root('xml')

来源：https://stackoverflow.com/questions/12296869/tsql-query-for-tree-view-control-and-remove-empty-elements-from-an-xml-file

标签

sql-server

tsql

treeview

xquery