XMLSEQUENCE

Syntax

Description of the illustration XMLSequence.gif

Purpose

XMLSequence has two forms:

• The first form takes as input an XMLType instance and returns a varray of the top-level nodes in the XMLType. This form is effectively superseded by the SQL/XML standard function XMLTable, which provides for more readable SQL code. Prior to Oracle Database 10g Release 2, XMLSequence was used with SQL function TABLE to do some of what can now be done better with the XMLTable function.

• The second form takes as input a REFCURSOR instance, with an optional instance of the XMLFormat object, and returns as an XMLSequence type an XML document for each row of the cursor.

Because XMLSequence returns a collection of XMLType, you can use this function in a TABLE clause to unnest the collection values into multiple rows, which can in turn be further processed in the SQL query.

Examples

The following example shows how XMLSequence divides up an XML document with multiple elements into VARRAY single-element documents. In this example, the TABLE keyword instructs Oracle Database to consider the collection a table value that can be used in the FROM clause of the subquery:

SELECT EXTRACT(warehouse_spec, '/Warehouse') as "Warehouse"
   FROM warehouses WHERE warehouse_name = 'San Francisco';

Warehouse
------------------------------------------------------------
<Warehouse>
  <Building>Rented</Building>
  <Area>50000</Area>
  <Docks>1</Docks>
  <DockType>Side load</DockType>
  <WaterAccess>Y</WaterAccess>
  <RailAccess>N</RailAccess>
  <Parking>Lot</Parking>
  <VClearance>12 ft</VClearance>
</Warehouse>

1 row selected.

SELECT VALUE(p)
   FROM warehouses w, 
   TABLE(XMLSEQUENCE(EXTRACT(warehouse_spec, '/Warehouse/*'))) p
   WHERE w.warehouse_name = 'San Francisco';

VALUE(P)
----------------------------------------------------------------
<Building>Rented</Building>
<Area>50000</Area>
<Docks>1</Docks>
<DockType>Side load</DockType>
<WaterAccess>Y</WaterAccess>
<RailAccess>N</RailAccess>
<Parking>Lot</Parking>
<VClearance>12 ft</VClearance>

8 rows selected.