Question

I have three tables table1, table2, table3 with col1, col2 and identity ID column. These table relationship are defined in the database.

I am trying to create a stored procedure that accepts xml string input and save that data into tables.

This is the XML input

<root>
 <table1 col1='a' col2='b'>
  <table2Array>
   <table2 col1='c' col2='d'>
    <table3array>
     <table3 col1='g' col2='h' />
     <table3 col1='i' col2='j' />
    </table3array>
   </table2>
  <table2 col1='c' col2='d'>
   <table3array>
    <table3 col1='k' col2='l' />
    <table3 col1='i' col2='j' />
   </table3array>
  </table2>
 </table2Array>
</table1>
 <table1 col1='a' col2='b'>
  <table2Array>
   <table2 col1='e' col2='f'>
    <table3array>
     <table3 col1='i' col2='j' />
     <table3 col1='i' col2='j' />
    </table3array>
   </table2>
   <table2 col1='e' col2='f'>
    <table3array>
     <table3 col1='g' col2='h' />
     <table3 col1='g' col2='h' />
    </table3array>
   </table2>
  </table2Array>
 </table1>
</root>

This xml is coming from a third party object and we don’t have control to modify the third party object to emit a different format xml.

Algorithm:

1. Loop through each node
2. Insert node attribute into table
3. Get last identity value
4. Call child nodes with last identity value as foreign key
5. Do until no more child nodes

Is this the only way to handle this situation? If so how to iterate through xml node?

Please help!!

Thanks,

Esen

Answer 1

Using merge and output you can do this without a loop using a technique described here.

I assume your table structure is like this.

create table Table1
(
  Table1ID int identity primary key,
  Col1 char(1),
  Col2 char(1)
)

create table Table2
(
  Table2ID int identity primary key,
  Table1ID int references Table1(Table1ID),
  Col1 char(1),
  Col2 char(1)
)

create table Table3
(
  Table3ID int identity primary key,
  Table2ID int references Table2(Table2ID),
  Col1 char(1),
  Col2 char(1)
)

The code

declare @T1 table (XMLCol xml, TargetID int);
declare @T2 table (XMLCol xml, TargetID int);

merge Table1 as T
using (select T1.XMLCol.query('*'),
              T1.XMLCol.value('@col1', 'char(1)'),
              T1.XMLCol.value('@col2', 'char(1)')
       from @XML.nodes('/root/table1') as T1(XMLCol)) as S(XMLCol, Col1, Col2)
on 1 = 0
when not matched then
  insert (Col1, Col2) values (S.Col1, S.Col2)
output S.XMLCol, inserted.Table1ID into @T1;          

merge Table2 as T
using (select T2.XMLCol.query('*'),
              T1.TargetID,
              T2.XMLCol.value('@col1', 'char(1)'),
              T2.XMLCol.value('@col2', 'char(1)')
       from @T1 as T1  
         cross apply T1.XMLCol.nodes('table2Array/table2') as T2(XMLCol)) as S(XMLCol, ID1, Col1, Col2)
on 1 = 0
when not matched then
  insert (Table1ID, Col1, Col2) values (S.ID1, S.Col1, S.Col2)
output S.XMLCol, inserted.Table2ID into @T2;          

insert into Table3(Table2ID, Col1, Col2)
select T2.TargetID,
       T3.XMLCol.value('@col1', 'char(1)'),
       T3.XMLCol.value('@col2', 'char(2)') 
from @T2 as T2
  cross apply T2.XMLCol.nodes('table3array/table3') as T3(XMLCol);

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