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XMLAGG function [Aggregate]

Generates a forest of XML elements from a collection of XML values.

XMLAGG( value-expression [ ORDER BY order-by-expression ] )

value-expression    An XML value. The content is escaped unless the data type is XML. The order-by-expression orders the elements returned by the function.

order-by-expression    An expression used to order the XML elements according to the value of this expression.

Any values that are NULL are omitted from the result. If all inputs are NULL, or there are no rows, the result is NULL. If you require a well-formed XML document, you must ensure that your query is written so that the generated XML has a single root element.

Data in BINARY, LONG BINARY, IMAGE, and VARBINARY columns is automatically returned in base64-encoded format when you execute a query that contains XMLAGG.

For an example of a query that uses the XMLAGG function with an ORDER BY clause, see Using the XMLAGG function.

• Using the XMLAGG function

• Part of the SQL/XML draft standard.

The following statement generates an XML document that shows the orders placed by each customer.

SELECT XMLELEMENT( NAME "order",
                   XMLATTRIBUTES( ID AS order_id ),
                     ( SELECT XMLAGG(
                         XMLELEMENT(
                           NAME "Products",
                           XMLATTRIBUTES( ProductID, Quantity AS "quantity_shipped" ) ) )
                      FROM SalesOrderItems soi
                      WHERE soi.ID = so.ID
                     )
                  ) AS products_ordered
FROM SalesOrders so
ORDER BY so.ID;