DB2 treats XQuery as a first-class language, allowing users to write Xquery expressions directly rather than requiring that users embed or wrap XQueries in SQL statements. DB2's query engine processes XQueries natively, meaning that it parses, evaluates, and optimizes XQueries without ever translating them into SQL behind the scenes. You can check http://www.ibm.com/developerworks/db...-0603saracco2/ to know how to use several popular SQL/XML expressions to query DB2 XML data XQuery.

Can I use Xquery and SQL both in single query in DB2?

Yes, you can write "bilingual" queries that include both XQuery and SQL expressions. DB2 will process and optimize these queries as well. To embed SQL in an XQuery, you use the db2-fn:sqlquery function in place of the db2-fn:xmlcolumn function. The db2 fn:sqlquery function executes an SQL query and returns only the selected data. The SQL query passed to db2-fn:sqlquery must only return XML data; this enables XQuery to further process the result of the SQL query. Please check http://www.ibm.com/developerworks/db...dm-0606nicola/ to know when to use SQL/XML or Xquery to query the XML data.

How to write and execute XQueries in DB2?

To execute an XQuery directly in DB2, you must preface the query with the keyword XQuery. This instructs DB2 to invoke its XQuery parser to process your request. You only need to do this if you are using XQuery as the outermost (or top level) language. If you embed XQuery expressions in SQL, you don't need to preface them with the XQuery keyword.

Can I embed XQueries in SQL?

How to validate XML data with a XML schema while inserting XML data?

This is answered in the XML Schema thread. Please refer to that thread.

yes, you can also embed XQueries in SQL. Indeed, DB2 9 features support for standard SQL/XML functions that are frequently used to formulate hybrid queries in which SQL is the outermost (or top-level) language. You can use XMLExists function for this. This function lets you navigate to an element (or other type of node) within your XML document and test for a specific condition. When specified as part of the SQL
WHERE clause, XMLExists restricts the returned results to only those rows that contain an XML document that satisfies your specified condition (where the specified condition evaluates to "true").

You can also use XMLQuery function which lets you project XML into the SQL result set returned from your SQL/XML query. It's commonly used to retrieve one or more elements from XML documents. Again, as you might imagine, the XMLQuery function takes an XQuery expression as input.