Database data to nested xml structure

Question

Hi All,
I need to convert the data in the oracle database to nested xml tree structure as below:
Data in the database is in the following structure:
1     branch1     13-JAN-11     a.txt
1     branch1     25-JAN-11     b.txt
1     branch1     25-JAN-11     c.txt
1     branch2     20-JAN-11     d.txt
2
XML for the above data should be in the format:
<Root>
<Account_no value="1">
<Desc value="branch1">
<Date value="13-JAN-11">
<Name value="a.txt"/>
</Date>
<Date value="25-JAN-11">
<Name value="b.txt"/>
<Name value="c.txt"/>
</Date>
</Desc>
<Desc value="branch2">
<Date value="20-JAN-11">
<Name value="d.txt"/>
</Date>
</Desc>
</Account_no>
<Account_no value="2">
</Account_no>
</Root>
I am able to get this kind of xml structure using java after storing the database data in a n-ary tree. But it takes more time to execute.
Can this kind of same xml format be achieved using pl/sql programming?
Please help me with your valuable insights.
Thanks,
Alagappan

Answer 1

Hi,
Please always mention your db version (select * from v$version).
Here's one solution using SQL/XML functions :
Sample data used :
create table sample_data
  account_no  number,
  description varchar2(30),
  dt          date,
  name        varchar2(30)
insert into sample_data values(1, 'branch1', to_date('13-JAN-11','DD-MON-RR'), 'a.txt');
insert into sample_data values(1, 'branch1', to_date('25-JAN-11','DD-MON-RR'), 'b.txt');
insert into sample_data values(1, 'branch1', to_date('25-JAN-11','DD-MON-RR'), 'c.txt');
insert into sample_data values(1, 'branch2', to_date('20-JAN-11','DD-MON-RR'), 'd.txt');
insert into sample_data values(2, 'branch3', to_date('20-JAN-11','DD-MON-RR'), 'e.txt');Query :
SELECT xmlserialize(document
         xmlelement("Root",
           xmlagg(
             xmlelement("Account_no", xmlattributes(account_no as "value"),
               xmlagg(
                 xmlelement("Desc", xmlattributes(description as "value"), dt)
                 order by description
             ) order by account_no
       as clob indent ) doc
FROM (
  SELECT account_no, description,
         xmlagg(
           xmlelement("Date", xmlattributes(to_char(dt,'DD-MON-RR') as "value"), name)
           order by dt
         ) dt
  FROM (
    SELECT account_no, description, dt,
           xmlagg(
             xmlelement("Name", xmlattributes(name as "value"))
             order by name
           ) name
    FROM sample_data
    GROUP BY account_no, description, dt
  GROUP BY account_no, description
GROUP BY account_no
DOC
<Root>
  <Account_no value="1">
    <Desc value="branch1">
      <Date value="13-JAN-11">
        <Name value="a.txt"/>
      </Date>
      <Date value="25-JAN-11">
        <Name value="b.txt"/>
        <Name value="c.txt"/>
      </Date>
    </Desc>
    <Desc value="branch2">
      <Date value="20-JAN-11">
        <Name value="d.txt"/>
      </Date>
    </Desc>
  </Account_no>
  <Account_no value="2">
    <Desc value="branch3">
      <Date value="20-JAN-11">
        <Name value="e.txt"/>
      </Date>
    </Desc>
  </Account_no>
</Root>
Here, I used XMLSerialize function with indent option to format the output (available starting with 11g).