How to check the information about the XML schemas in the XSR?

DB2 stores information about XML Schemas in a system catalog view SYSCAT.XSROBJECTS. This view can be queried to retrieve information like the object schema, object name, target namespace, and schema location. The actual schema documents are stored in catalog SYSCAT.XSROBJECTCOMPONENT. The SYSCAT.XSROBJECTS catalog view contains 1 row per XML Schema. On the other hand, SYSCAT.XSROBJECTCOMPONENT catalog has 1 row per schema document.
You can use following queries to get the information:

SELECT objectschema, objectname, targetnamespace, schemalocation FROM syscat.xsrobjects
SELECT objectschema, objectname, targetnamespace, schemalocation from syscat.xsrobjectcomponents

And how do I drop a registered schema?

A registered schema can be dropped by using Drop XSRObject command. The schema repository does not have a notion of individual schema documents. It only has a notion of an XML Schema, which is a collection of 1 or more schema documents. Thus, to drop an XSR Object implies deleting all schema documents associated with that XSR Object.

Can you give a sample query for using XMLNamespaces functions?

Below example generates an "employee" element for each employee. The employee element is associated with XML namespace "urn:bo', which is bound to prefix "bo". The element contains attributes for names and a hiredate subelement.

SELECT e.empno, XMLSERIALIZE(XMLELEMENT(NAME "bo:employee",
XMLNAMESPACES('urn:bo' as "bo"), XMLATTRIBUTES(e.lastname, e.firstnme), XMLELEMENT(NAME "bo:hiredate", e.hiredate)) AS CLOB(50)) FROM employee e where e.edlevel = 12;

The result of the query would be similar to the following result:

<bo:employee xmlns:bo="urn:bo" LASTNAME="PARKER" FIRSTNME="JOHN">
<bo:hiredate>198-5-3</bo:hiredate></bo:employee><bo:employee
xmlns:bo="urn:bo"
LASTNAME="SETRIGHT"FIRSTNME="MAUDE"><bo:hiredate>1964-9-12</bo:hiredate></bo:employee>


Another example: generate two elements for each employee using XMLFOREST. The first "lastname" element is associated with the default namespace "http://hr.org", and the second "job" element is associated with XML namespace "http://fed.gov", which is bound to prefix "d".

SELECT empno, XMLSERIALIZE(XMLFOREST(XMLNAMESPACES(DEFAULT 'http://hr.org', 'http://fed.gov' AS "d"),lastname, job AS "d:job") AS CLOB(50)) FROM employee where edlevel = 12;

The result of the query would be similar to the following result:

<LASTNAME xmlns=http://hr.org xmlns:d="http://fed.gov
">PARKER</LASTNAME><d:job xmlns="http://hr.org" xmlns:d="http://fed.gov">OPERATOR</d:job>
<LASTNAME xmlns="http://hr.org"
xmlns:d="http://fed.gov">SETRIGHT</LASTNAME><d:job xmlns="http://hr.org" xmlns:d="http://fed.gov">OPERATOR</d:job>

MTK can be downloaded at
http://www-306.ibm.com/software/data/db2/migration/mtk/. More information can be found at
http://www-1.ibm.com/support/docview...id=swg27009230.

Could you please explain how DB2 validate XML documents against DTDs?

You can’t validate XML document against DTDs; DTDs validation not supported. You can validate your XML document against XML schemas only. You can still insert documents that contain a DOCTYPE or that refer to DTDs.

There are tools available, such as those in IBM Rational Application Developer that help you generate XML schemas from various sources, including DTDs, existing tables, or XML documents.

Before you can validate, you must register your XML schema with the built-in XML schema repository (XSR). This process involves registering each XML schema document that makes up the XML schema. Once all XML schema documents have been successfully registered, you must complete the registration. One method of registering an XML schema is through commands.

Register and complete registration of the posample.customer XML schema as follows, providing the absolute path to the sqllib/samples/xml directory on your system:
REGISTER XMLSCHEMA 'http://posample.org' FROM 'file:///<c:/sqllib/samples/xml>customer.xsd' AS posample.customer COMPLETE

You can verify that the XML schema was successfully registered by using follow query:

SELECT OBJECTSCHEMA, OBJECTNAME FROM SYSCAT.XSROBJECTS

MTK can be downloaded at
http://www-306.ibm.com/software/data/db2/migration/mtk/. More information can be found at
http://www-1.ibm.com/support/docview...id=swg27009230.

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

The following INSERT statement inserts a new XML document into the Info column of the Customer table, only if the document is valid according to the posample.customer XML schema previously registered.

INSERT INTO Customer(Cid, Info) VALUES (1003, XMLVALIDATE (XMLPARSE (DOCUMENT
'<customerinfo xmlns="http://posample.org" Cid="1003">
<name>Robert Shoemaker</name>
<addr country="Canada">
<street>1596 Baseline</street>
<city>Aurora</city>
<prov-state>Ontario</prov-state>
<pcode-zip>N8X 7F8</pcode-zip>
</addr>
<phone type="work">905-555-7258</phone>
<phone type="home">416-555-2937</phone>
<phone type="cell">905-555-8743</phone>
<phone type="cottage">613-555-3278</phone>
</customerinfo>' PRESERVE WHITESPACE )
ACCORDING TO XMLSCHEMA ID posample.customer ))

XMLVALIDATE operates on XML data. Because the XML document in this example is passed as character data, and character data can only be assigned directly to XML in INSERT, UPDATE, or DELETE statements, the XMLPARSE function must be used in this case. The XMLPARSE function parses its argument as an XML document and returns an XML value.

To verify that the validation and insert were successful, query the Info column:

SELECT Info FROM Customer
This query should return three XML documents, one of which is the document just inserted.