PL/SQL DBMS_XMLSTORE.updateXML

Oracle PL/SQL’s DBMS_XMLSTORE package provides a convenient way to perform operations on XML data directly within the database. The updateXML function is a part of this package, designed to update existing rows in a table based on the XML content provided. This function is particularly useful when you have XML data that you want to map to a relational table for updating purposes, enabling seamless integration of XML data sources with relational database operations.

Overview

The DBMS_XMLSTORE.updateXML function updates rows in a table or view using an XML document. The function identifies the rows to be updated based on a primary key or unique constraint specified in the XML. It then updates these rows with the values provided in the XML document. This is particularly useful for batch updates where the data to be updated is available in XML format.

Syntax

DBMS_XMLSTORE.updateXML(
   ctx IN dbms_xmlstore.ctxType,
   xmldoc IN CLOB
) RETURN NUMBER;

ctx: The context handle returned by DBMS_XMLSTORE.newContext. This context specifies the table or view to be updated.
xmldoc: The XML document containing the data for updating rows. The structure of the XML document must match the table structure defined in the context.

Return Value

The function returns the number of rows updated.

Usage

Create Context: First, you need to create a context for the specific table or view you want to update. Use DBMS_XMLSTORE.newContext to create this context.

Set Key Column: Optionally, you can set the key column(s) that identify the row to be updated using DBMS_XMLSTORE.setKeyColumn.

Update XML: Call DBMS_XMLSTORE.updateXML with the context and the XML document as arguments.

Close Context: After completing the updates, close the context using DBMS_XMLSTORE.closeContext to release resources.

Example

DECLARE
  l_ctx  dbms_xmlstore.ctxType;
  l_rows NUMBER;
BEGIN
  l_ctx := dbms_xmlstore.newContext('my_table'); -- Specify your table name
  dbms_xmlstore.setKeyColumn(l_ctx, 'ID'); -- Assuming 'ID' is the primary key

  l_rows := dbms_xmlstore.updateXML(l_ctx, '<ROWSET><ROW><ID>1</ID><NAME>New Name</NAME></ROW></ROWSET>');

  dbms_output.put_line(l_rows || ' rows updated.');

  dbms_xmlstore.closeContext(l_ctx);
END;

This example demonstrates updating a row in my_table where the ID is 1, setting the NAME column to ‘New Name’. The updateXML function can update multiple rows in a single call if the XML document contains multiple elements.

Considerations

The XML document must be well-formed and match the structure expected by the table or view.
The function performs updates based on the primary key or unique constraint; therefore, these keys must be present in the XML document.
Proper error handling should be implemented to manage scenarios where the XML document is malformed or does not match the table structure.

The DBMS_XMLSTORE.updateXML function provides a powerful mechanism for integrating XML data updates into relational tables, enabling efficient batch updates and seamless data integration within Oracle databases.