Building XML from relational data

Question

I need to create XML documents from relational data that conforms to an XML schema document. We need to store and query the XML documents we create.
Therefore, we have decided to store the XML using the object model rather than as a CLOB
i.e. register the schema with the XML DB which in turn creates the tables and object types that represent the schema.
What is the best way build the XML document from the relational data ??
Can I pass the relational data to the default constructors of the object types created by the schema registration ?? (and then create an XML document from the top level object instance using SYS_XMLGEN)
Or should I build the xml from strings using XMLELEMENT,XMLFOREST built-in's when retrieving the data from the relational tables ?? OR use the XMLDOM package to build the document ??
Would appreciate any advice on the best approach.

Answer 1

There are basically two ways to join your document fragments with SQLX:
1/. With xmlForest
e.g. SELECT XMLELEMENT ( "Emp",XMLForest(e.employee_id, e.lname, e.salary)) AS "result"
FROM employees e WHERE employee_id > 1500 ;
result
<Emp>
< employee_id >1769</ employee_id >
< lname >Smith</ lname >
< salary >200000</ salary >
</Emp>
2/. With nested invocations of xmlElement
e.g. SELECT XMLELEMENT("Emp", XMLELEMENT("name", e.fname ||' '|| e.lname),
XMLELEMENT ( "hiredate", e.hire)) AS "result"
FROM employees e WHERE employee_id > 200 ;
result
<Emp>
<name>John Smith</name>
<hiredate>2000-05-24</hiredate>
</Emp>
<Emp>
<name>Mary Martin</name>
<hiredate>1996-02-01</hiredate>
</Emp>