XML DB: is it possible to get a row for each element in a container element?

Question

I have an XML document containing a container element (collection). If I query, using an XPath expression, the contained elements I get a row for each container element with the contained element concatenated. Is it possible to get a row for each contained element?
I run this simple query:
select extract(xmltype('<colors><color>Red</color><color>Green</color></colors>')
, '/colors/color/text()').getstringval() from dual
And get this result:
EXTRACT(XMLTYPE('<COLORS><COLOR>RED</COLOR><COLOR>GREEN</COLOR></COLORS>'),'/COL
RedGreen
1 row selected.
What I would like to have is:
Red
Green
2 rows selected.
Wishful thinking or possible? Many thanks!

Answer 1

Sure. This is where our XMLSequence() function comes in. It allows you to treat the top-level nodes in a nodeset as if they were rows in a table when combined with the TABLE() operator. Here's an example.
First, to make the SQL look a little cleaner, I like to define a function like this:
create or replace function testdoc return xmltype as
begin
  return xmltype('<colors><color>Red</color><color>Green</color></colors>');
end;.
To break out the nodeset of <color> elements as a table, we use the following query:
select value(list_of_color_elements).extract('*/text()').getStringVal() as color
from TABLE( XMLSequence( extract(testdoc(),'/colors/color'))) list_of_color_elements.
Or, using the new-in-9.2 extractValue() operator so we don't have to remember the text() part:
select extractValue( value(list_of_color_elements), '.') as color
from TABLE( XMLSequence( extract( testdoc() ,'/colors/color'))) list_of_color_elements.
Here the TABLE(XMLSequence(...)) combo produces a table of XMLType, with one XMLType object in each row of the table.
In general, if the XMLType instance were coming from an XMLType table xmltab the query would look like this:
select extractValue( value(colors), '.') as color
from xmltab x, /* Important that this table comes earlier in the FROM clause! */
     TABLE( XMLSequence( extract( value(x),'/colors/color'))) colors.
And if the XMLType were instead in a column of XMLType named doc in a table xmltab, then we would have the syntax:
select extractValue( value(colors), '.') as color
from xmltab x, /* Important that this table comes earlier in the FROM clause! */
     TABLE( XMLSequence( extract( x.doc ,'/colors/color'))) colorsOnce you get the hang of it, you'll see that the combination of TABLE(XMLSequence()) to "shred" XML nodes into rows, and XMLAgg() to aggregate fragments of XML across multiple rows back into a single document, is quite powerful.