Oracle PL/SQL’s DBMS_XMLQUERY.setRowSetTag function is a part of the DBMS_XMLQUERY package, which facilitates generating XML data from SQL queries. This function specifically allows users to customize the XML output by setting a custom tag name for the rowset element in the resulting XML. The rowset element is the parent tag that encapsulates the rows returned by the query.
Syntax
The basic syntax for DBMS_XMLQUERY.setRowSetTag is as follows:
DBMS_XMLQUERY.setRowSetTag(ctx IN OUT NOCOPY CLOB, rowsetTag IN VARCHAR2);
ctx: The context handle returned by DBMS_XMLQUERY.NEWCONTEXT. This context is used throughout to manage the state of XML generation.
rowsetTag: The custom tag name you want to use for the rowset.
Usage
Before you can use DBMS_XMLQUERY.setRowSetTag, you must first initialize a context with DBMS_XMLQUERY.NEWCONTEXT, passing your SQL query as a parameter. Once the context is initialized, you can call setRowSetTag to set a custom tag name for the rowsets in your XML output.
Here is a simple example of how to use DBMS_XMLQUERY.setRowSetTag:
DECLARE
ctx CLOB;
xml CLOB;
BEGIN
ctx := DBMS_XMLQUERY.newContext('SELECT * FROM employees'); -- Initialize the context with a query
DBMS_XMLQUERY.setRowSetTag(ctx, 'Employees'); -- Set custom rowset tag
xml := DBMS_XMLQUERY.getXML(ctx); -- Retrieve the XML
DBMS_XMLQUERY.closeContext(ctx); -- Always close the context when done
-- Process the XML output stored in 'xml'
END;
Considerations
The DBMS_XMLQUERY.setRowSetTag function must be called after initializing the context with DBMS_XMLQUERY.NEWCONTEXT and before retrieving the XML data with DBMS_XMLQUERY.GETXML.
Customizing the rowset tag can be particularly useful when you need the XML output to adhere to specific schema definitions or when improving the readability of the XML data.
Remember to close the context with DBMS_XMLQUERY.CLOSECONTEXT to release resources allocated for the XML generation process.
By allowing customization of the rowset tags, Oracle PL/SQL provides developers with greater control over the structure and presentation of XML data generated from SQL queries, making it easier to integrate with other systems and processes that consume XML.