Enhanced XML Support in DB2 for LUW

Transcription

1 extra on Demand Enhanced XML Support in DB2 for LUW Speaker Name David Owen (DOCE) Session: H12 Thursday May 26 th :30am 1

2 Agenda XML support in the DB2 Family XML extender for decomposing XML documents XML publishing functions and expressions Building XML functionality in your SQL statement Xquery for querying XML 2 Abstract XML data is the defacto data standard for many web based and ERM solutions. This presentation looks at the new functionality within DB2 V8 to support XML. It includes the new XML publishing functions as well as the enhancements to the XML extender. It also provides examples of using this new functionality and projected costs. We also take a brief look at querying our XML data in DB2 using Xquery. Bullet Points: 1. XML support in the DB2 family 2. XML extender for decomposing XML docs 3. XML publishing functions and expressions 4. Building XML functionality in your SQL statements 5. Xquery for querying XML 2

3 XML support in the DB2 Family LUW XML publishing functions 8.1 & 8.2 XML extender z/os XML publishing functions V8 XML extender iseries XML publishing functions V5R2 XML extender Future support XML engine in DB2 3 XML support has been available in DB2 with the XML extender since V7.1 of UDB for LUW. XML publishing functions were introduced in V8 for LUW and z/os Vnext should see an XML engine in DB2 with separate structures and support from the relational database. 3

4 XML extender Provides support for storing and composing XML data in a DB2 database Is now part of the DB2 engine Enabled with dxxadm commands <?xml version="1.0"?> <!DOCTYPE Order SYSTEM "dxx_install/samples/db2xml/dtd/get start.dtd" > <Order key="1"> <Customer> <Name>American Motors</Name> < >parts@am.com</ > </Customer> <Part color="black "> <key>68</key> <Quantity>36</Quantity> <ExtendedPrice> </Extende dprice> <?xml version="1.0"?> <!DOCTYPE Order SYSTEM "dxx_install/samples/db2xml/dtd/get <Tax> e-02</Tax> start.dtd" > <Order key="1"> <Customer> <Name>American Motors</Name> < >parts@am.com</ > </Customer> <Part color="black "> <key>68</key> <Quantity>36</Quantity> <ExtendedPrice> </Extende dprice> <Tax> e-02</Tax> Decomposing Composing 4 The XML extender allows you to combine XML data and relational data in a single database. It allows you to store XML documents in a DB2 database as well as compose XML documents from the database. It also provides fast search on data within the XML documents. The XML extender provides storage and access methods for the XML documents. Administration tools are available to manage the integration of XML data in relational tables. It provides support for Document Type Definition (DTD) files and XML schemas. Specific to the XML extender is the Document Access Definition (DAD) file that controls mapping. Since V8, the XML extender is built in to the DB2 engine. User defined functions and stored procedures provide the features and support. 4

5 XML functions Storage functions To insert XML documents into a database Retrieval functions Overloaded function Content() used for retrieval Retrieve from external server storage to internal client host variable Retrieval from internal storage to external server file Extraction functions Extract element content or attribute value from XML document and return SQL data types XML UDT and location path required 5 The XML extender contains a number of functions. These can be divided into the following classes: Storage functions XML storage functions can be used to insert XML documents into a DB2 database. This can be done using the default casting functions of a UDT in an INSERT or SELECT statement. It can generate any of the XML data types XMLCLOB, XMLVARCHAR or XMLFILE. Retrieval functions Retrieval of XML documents can be used to retrieve data as XML documents. This is done using the overloaded Content function which can retrieve data from XMLCLOB, XMLVARCHAR columns and XMLFILE. It uses default casting. Extraction functions Extract the element or attribute from xml document and returns SQL data types. This requires location path of the element or attribute. This can be used for all data types except Decimal 5

6 XML functions Update function - Update() Updates a specified element or attribute in XML document Supports attributes in location path predicates but not elements /ORDER/PART[@colour= RED ] supported /ORDER/PART/[SHIPDATE < 25/2/04 Validate functions Schema validation SVALIDATE() DTD validation DVALIDATE() 6 The XML update( ) function updates a specified element or attribute value in 1 or more XML documents stored in the XML column. It supports location paths that have predicates with attributes, but not elements. XML validation functions include: Schema validation SVALIDATE() this will return 1 if valid 0 if not valid DTD validation DVALIDATE() this will return 1 if valid 0 if not valid The output will be written to the xml extender trace file if it fails. Ensure that the XML extender trace is on before validation. 6

7 MQ support MQ functions Allow querying of XML documents and publish results to message queue Can retrieve XML documents from message queues, decompose it and store in DB2 tables Compose XML documents from DB2 data and send to MQ queues MQ stored procedures Composition generate XML documents using data in existing tables and send XML documents to a message queue Decomposition break down/ shred incoming XML from message queue to DB2 tables 7 In UDB 8.2 support for MQ is available. MQ functions will allow you to query XML data and publish results in a message queue The MQ functions enable you to query XML documents and publish the results to a queue. In addition you can also retrieve an XML document from a message queue, decompose it and store the data in a DB2 table. The stored procedures allow you to retrieve XML document from message queues and store it as untagged data in the database. Stored procedures can also compose the data from DB2 data and send the document to an MQ message queue. 7

8 DAD Checker Downloadable java application Checks the validity of a DAD for XML collections only It ensures the DAD is semantically correct Checks well formed and DTD validation Duplicate element and leaf (attribute) detection Missing attribute or table detection Missing text /attribute nodes Attribute and element node mapping order check Data mapping consistency check for tags Additional checks 8 The DAD checker is used to verify the validity of DAD files that use the XML extender collection storage method. It validates the mapping between the tables and the XML document structure. It ensures that a DAD file is semantically correct. To execute it: Java dadchecker.check_dad_xml It checks for well formedness and DTD validation. It checks for duplicate (attribute node) and leaf (element node) detection It checks for missing type attribute detection It checks for missing table declaration It checks for missing text node and attribute node detetction It checks for attribute nde and element node mapping order check Data mapping consistency check for tags It checks for multi-occurrence attribute value checking It checks for attribute and element potential naming conflicts 8

9 XSLT translation Can translate XML to HTML using XSLT translation XSLTransformtoFile function XSLTransformotCLOB function SELECT XSLTransformToFile( xmlobj, /dxx_install/db2xml/xslt/order.xsl, /dxx_install/db2xml/html/order.ht ml ) FROM xslt_tab Orderkey : 1 Customer Name : American Motors, parts@am.com, Parts Color : black, key : 68, Quantity : 36, ExtendedPrice : , Tax : e-2, Shipment ShipDate : , ShipMode : BOAT, Shipment ShipDate : , ShipMode : AIR, Parts Color : red, key : 128, Quantity : 28, ExtendedPrice : , Tax : e-2, Shipment ShipDate : , ShipMode : TRUCK, 9 XSLT is a stylesheet for XML documents. It can be used to apply formatting rules to each of the elements in an XML document. XSLT stylesheets are XML documents. XSLT allows you to transform XML structure into data types by removing or replacing XML tags. The steps are: Create an XML file in result table Create a style sheet Use the XSLTranformtoFile function to create an HTML file Use the XSLTransformtoCLOB function to transform the document into a CLOB 9

10 XML publishing functions and expressions Can create XML documents from relational data Used in SQL expressions with embedded XML expressions XMLELEMENT XMLATTRIBUTES XMLAGG XMLFOREST XMLCONCAT They can be used almost anywhere that you can write SQL 10 In V8, XML publishing functions are now available within the DB2 engine. These supersede the composition and publishing functions available in earlier releases of the XML extender. These allow you to create XML elements and XML documents directly from DB2 data using SQL/XML functions. The functions can be written in almost any SQL statement. 10

11 XML2CLOB / XMLSERIALIZE XML2CLOB for materialising data for external publication XMLSERIALIZE replaces XML2CLOB (applies to LUW but XML2CLOB still valid in z/os) 11 XML data is not stored as an XML data type within DB2. The data has to be externalised to an external data type XMLCLOB, XMLVARCHAR or XMLFILE. XML2CLOB converts the internal data type to an external data type. XMLSERIALIZE should be used instead to serialise the data into XML external data type. 11

12 XMLELEMENT Constructs an XMLEMENT from the arguments supplied by columns or expressions Used to define element(s) within XML document Comprised from columns or expressions from DB2 data 12 The XMLELEMENT function allows SQL to create an XML element in an XML document. The XMLELEMENT name is based on one or more arguments from the relational data. It must be an XML Qname. If it is qualified, the namespace prefix must be declared. It can contain optional namespace declarations and optional attributes. 12

13 XMLELEMENT example SELECT e.empno, XMLSERIALIZE (CONTENT XMLELEMENT(NAME "Emp", XMLELEMENT(NAME "name", e.firstnme '' e.lastname), XMLELEMENT(NAME "hiredate", e.hiredate), XMLELEMENT(NAME "DEPT", e.workdept), XMLELEMENT(NAME "JOB", e.job) ) AS CLOB) AS "Result" FROM employee e WHERE e.edlevel = 12; <Emp><name>JOHNPARKER</name> <hiredate> </hiredate> <DEPT>E11</DEPT> <JOB>OPERATOR</JOB></Emp> <Emp><name>MAUDESETRIGHT</name> <hiredate> </hiredate> <DEPT>E11</DEPT> <JOB>OPERATOR</JOB></Emp> 13 13

14 XMLATTRIBUTES Constructs XMLATTRIBUTES from the arguments specified An attribute is created for the XMLELEMENT The attributes are specific to that XMLELEMENT Cannot be used without an XMLELEMENT 14 The XMLATTRIBUTES function allows you to construct attributes from arguments. The attributes created are specific to that XMLELEMENT and only for that ELEMENT 14

15 XMLATTRIBUTES example SELECT e.empno, XMLSERIALIZE (CONTENT XMLELEMENT(NAME "Emp", XMLATTRIBUTES(e.firstnme '' e.lastname AS "name", e.hiredate AS "hiredate", e.workdept AS "DEPT", e.job AS "JOB") ) AS CLOB) AS "Result" FROM employee e WHERE e.edlevel = 12; <Emp name="johnparker" hiredate=" " DEPT="E11" JOB="OPERATOR"></Emp> <Emp name="maudesetright" hiredate=" " DEPT="E11" JOB="OPERATOR"></Emp> 15 15

16 XML NAMESPACES Collection of names identified by a URI reference. Used in XML documents as element types and attributes Can be used in XMLELEMENT of XMLFOREST 16 An XML namespace is a collection of names, identified by a URI reference, which are used in XML documents as element types and attribute names. Predefined prefixes exist for namespaces. These can represent a pre-defined XML vocabulary. The URI is pre-bound to a prefix. This reduces the size of the URI when defining the namespace within the element or attribute. The predefined namespace prefix xml can be used without the need to define it. In addition you can define your own prefix 16

17 XML NAMESPACES example SELECT emp.empno, XMLSERIALIZE(CONTENT XMLELEMENT(NAME "employee", XMLNAMESPACES(DEFAULT ' emp.lastname, XMLELEMENT(NAME "job", XMLNAMESPACES(NO DEFAULT), emp.job, XMLELEMENT(NAME "department", XMLNAMESPACES(DEFAULT ' emp.workdept))) AS CLOB) AS "Result" FROM employee emp WHERE emp.edlevel = 12; <employee xmlns=" xmlns=""> OPERATOR<department xmlns=" </job></employee> <employee xmlns=" xmlns=""> OPERATOR<department xmlns=" </job></employee> 17 17

18 XMLFOREST Constructs a list ( forest ) of XML Elements from the list of expressions The XML elements are all nested inside the main element Can also provide the same function using nested XMLELEMENTs 18 The XMLFOREST function creates a list ( forest ) of XML elements that all share a specific pattern from a list of expressions, one element for each argument. The same function can also be provided by nesting XMLELEMENTs. 18

19 XMLFOREST example SELECT e.empno, XMLSERIALIZE (CONTENT XMLELEMENT(NAME "Emp", XMLFOREST(e.firstnme '' e.lastname AS "name"), XMLFOREST(e.hiredate AS "hiredate"), XMLFOREST(e.workdept AS "DEPT"), XMLFOREST(e.job AS "JOB") ) AS CLOB) AS "Result" FROM employee e WHERE e.edlevel = 12; <Emp><name>JOHNPARKER</name> <hiredate> </hiredate> <DEPT>E11</DEPT> <JOB>OPERATOR</JOB></Emp> <Emp><name>MAUDESETRIGHT</name> <hiredate> </hiredate> <DEPT>E11</DEPT> <JOB>OPERATOR</JOB></Emp> 19 19

20 XMLAGG Returns the concatenation of a set of XML values It produces a single aggregated row for all the rows in the query The ORDER BY specifies the ordering of the rows from the same grouping set in the aggregation. 20 The XMLAGG function returns a concatenation of XML elements. The XMLAGG function has one argument with an optional ORDER BY clause. The ORDER BY clause specifies the ordering of the rows from the same grouping set to be processed in the aggregation. If the ORDER BY clause is not specified or the ORDER BY clause cannot differentiate the order of the sort key value, then the order of rows from the same group to be processed in the aggregation is arbitrary. 20

21 XMLAGG example SELECT e.empno, XMLSERIALIZE (CONTENT XMLELEMENT(NAME "Emp", XMLAGG(XMLELEMENT(NAME "name", e.firstnme '' e.lastname)),xmlagg(xmlelement(name "hiredate", e.hiredate) order by e.hiredate),xmlagg(xmlelement(name "DEPT", e.workdept) order by e.workdept) ) AS CLOB) AS "Result" FROM employee e WHERE e.workdept in ('A01','B11','C01','E21') GROUP BY e.empno, e.hiredate; <Emp><name>JOHNPARKER</name> <hiredate> </hiredate> <DEPT>E11</DEPT></Emp> <Emp><name>MAUDESETRIGHT</name> <hiredate> </hiredate> <DEPT>E11</DEPT></Emp> 21 21

22 XMLCONCAT Return a forest of XML elements from concatenation of arguments 22 The XML CONCAT function returns a forest of XML elements that are generated from concatenating 2 or more arguments. The forest is an ordered set of sub-trees of XML nodes 22

23 XMLCONCAT example SELECT e.empno, XMLSERIALIZE(CONTENT XMLCONCAT(XMLELEMENT(NAME "firstname", e.firstnme), XMLELEMENT(NAME "lastname", e.lastname)) AS CLOB) AS "Result" FROM employee e WHERE e.edlevel = 12; <firstname>john</firstname> <lastname>parker</lastname> <firstname>maude</firstname> <lastname>setright</lastname> 23 23

24 XML in INSERT insert into empxml select empno,firstnme,midinit,lastname,workdept,phoneno,hiredate,job,edlevel,sex,birthdate,salary,bonus,comm, XMLSERIALIZE (CONTENT XMLELEMENT(NAME "Emp", XMLELEMENT(NAME "name", firstnme '' lastname), XMLELEMENT(NAME "hiredate", hiredate), XMLELEMENT(NAME "DEPT", workdept), XMLELEMENT(NAME "JOB", job) ) AS CLOB) from employee; 24 SQL/XML can be used within many SQL statements. In this case, the XML functions are used to create an XML document that will be stored in an XML enabled column in a table. 24

25 XML in JOIN SELECT e.empno, XMLSERIALIZE (CONTENT XMLELEMENT(NAME "Emp", XMLELEMENT(NAME "name", e.firstnme '' e.lastname), XMLELEMENT(NAME "hiredate", e.hiredate), xmlelement(name "deptnum", e.workdept), xmlelement(name "deptname", d.deptname)) AS CLOB) AS "Result" FROM employee e, department d WHERE e.edlevel = 12 and e.workdept=d.deptno; <Emp><name>JOHNPARKER</name> <hiredate> </hiredate><deptnum>e11</deptnum> <deptname>operations</deptname> </Emp> <Emp><name>MAUDESETRIGHT</name> <hiredate> </hiredate><deptnum>e11</deptnum> <deptname>operations</deptname> </Emp> 25 25

26 XML in UNION SELECT 'emp type1',xmlserialize(content XMLELEMENT(NAME "Department", XMLATTRIBUTES(e.workdept AS "name"), XMLAGG(XMLELEMENT(NAME "emp", e.lastname) ORDER BY e.lastname ) ) AS CLOB ) AS "dept_list1" FROM employee e WHERE e.workdept IN ('C01','E21') GROUP BY workdept UNION ALL SELECT 'emp type 2',XMLSERIALIZE(CONTENT XMLELEMENT(NAME "Department", XMLATTRIBUTES(e.workdept AS "name"), XMLAGG(XMLELEMENT(NAME "emp", e.lastname) ORDER BY e.lastname ) ) AS CLOB ) AS "dept_list2" FROM employee e WHERE e.workdept IN ('B01','A00','D11') group by workdept; 26 26

27 XML in UNION emp type 2 <Department name="a00"> <emp>haas</emp><emp>lucchessi</emp><emp>o'connell</emp> </Department> emp type 2 <Department name="b01"> <emp>thompson</emp> </Department> emp type 2 <Department name="d11"> <emp>adamson</emp><emp>brown</emp><emp>jones</emp><emp>lutz</emp> <emp>pianka</emp><emp>scoutten</emp><emp>stern</emp><emp>walker</e mp><emp>yoshimura</emp> </Department> emp type1 <Department name="c01"> <emp>kwan</emp><emp>nicholls</emp><emp>quintana</emp> </Department> emp type1 <Department name="e21"> <emp>gounot</emp><emp>lee</emp><emp>mehta</emp><emp>spenser</emp> </Department> 27 27

28 XML in NTE select xmlserialize(content xmlelement(name "emp", xmlelement(name "dept", e.workdept), xmlelement(name "avgsalary", e.avgsal)) AS CLOB) AS "Result" from (select workdept, avg(salary) as avgsal from employee group by workdept) e; <emp><dept>a00</dept><avgsalary> </avgsalary></emp> <emp><dept>b01</dept><avgsalary> </avgsalary></emp> <emp><dept>c01</dept><avgsalary> </avgsalary></emp> <emp><dept>d11</dept><avgsalary> </avgsalary></emp> <emp><dept>d21</dept><avgsalary> </avgsalary></emp> <emp><dept>e01</dept><avgsalary> </avgsalary></emp> <emp><dept>e11</dept><avgsalary> </avgsalary></emp> <emp><dept>e21</dept><avgsalary> </avgsalary></emp> 28 This SQL/XML statement will use a Nested table expression as input for publishing an XML document. 28

29 XML in a Subquery select empno, name,salary, XMLSERIALIZE (CONTENT XMLELEMENT(NAME "Emp", XMLELEMENT(NAME "name", firstnme '' lastname), XMLELEMENT(NAME "hiredate", hiredate)) AS CLOB) AS "Result1" from employee where Result1 in (select XMLSERIALIZE (CONTENT XMLELEMENT(NAME "Emp", XMLELEMENT(NAME "name", firstnme '' lastname), XMLELEMENT(NAME "hiredate", hiredate)) AS CLOB) AS "Result2" from employee where workdept = 'A00'); <Emp> <name>philipsmith</name> <hiredate> </hiredate> </Emp> 29 In this example, the XML document generated from the Outer query is used to correlate against the results from the inner query. 29

30 Complex XML SELECT VARCHAR( XML2CLOB( XMLElement(NAME "TABLE", XMLATTRIBUTES('1' as "border"), XMLElement(NAME CAPTION, 'Department-Employee Table'), XMLElement(NAME TR, XMLFOREST('Dept No' as TH, 'Dept Name' as TH, 'Emp No' as TH, 'Emp Name' as TH, 'Phone' as TH) ), XMLAGG(XMLCONCAT(XMLELEMENT(NAME TR, XMLELEMENT(NAME TD, XMLATTRIBUTES( X.CNT+1 as rowspan"),d.deptno), XMLELEMENT(NAME TD, XMLATTRIBUTES( X.CNT+1 as "rowspan"),d.deptname) ), ( SELECT XMLAGG(XMLElement(NAME TR, XMLForest(EMPNO as TD, FIRSTNME ' ' LASTNAME as TD, PHONENO as TD) ) ) FROM employee E WHERE E.WORKDEPT = D.DEPTNO ) ) ) ) ) ) FROM department D, (SELECT WORKDEPT, COUNT(*) FROM employee GROUP BY WORKDEPT) X(DEPTNO, CNT) WHERE D.DEPTNO = X.DEPTNO AND D.DEPTNO IN ('A00', 'C01'); 30 30

31 SQL/XML performance Composition Sub-second cpu and elapsed time Based on z990 5 processors Comparison with XML extender SQL/XML publishing Many times faster than XML extender 31 31

32 SQL/XML considerations The cost is dependent on the complexity and level of XML tagging Small and simple SQL/XML statements The overhead is minimal Deeply nested XML documents with dozens of XML functions Can be up to 3* - 4* slower than relational equivalent Excessive use of XMLAGG is costly Benefit get thick fully tagged XML documents ** BUT IT IS NOT ALL BAD NEWS ** 32 32

33 SQL/XML performance improvements If the SQL returns large number of rows with many rows returned for many others in 1 to Many relationships Eg Line items are returned for every order In XML this can perform significantly better The line items are nested under the original order Less data is returned Can be improvement up to 3* - 4* faster than relational query 33 33

34 Web services from DB2 Enhanced e-business application functionality based on Simple Object Access Protocol and XML DADX support WSDL Web Services Description Language WORF framework provides simple mapping of XML to SQL Access to web services via DADX using SQL calls or stored procedure 34 Web services provide access to distributed applications. They are used to integrate information processing between and within enterprises. They can access both services and also relational data. The web service infrastructure is based on XML and data flow between requestor and provider using XML. It is created by wrapping an application such that it an be accessed using standard XML messages. The XML message are contained in SOAP The Web services Description Language (WSDL) is an XML vocabulary to automate the details involved in communicating between web services applications. The Web services Object Runtime Framework (WORF) provides an environment to create simple web services that access DB2. It uses SOAP and Document Access Definition Extension (DADX) files. The DADX document shows to create the web service using a set of operations defined by SQL statements, stored procedure calls and also XML extender DAD files. 34

35 Web service architecture SOAP requests SOAP Service Runtime WORF DADX processor SOAP Service Runtime WORF DADX processor DADX SELECT * FROM TABLE Call procedure() DADX Tables Stored Procedures 35 35

36 DADX file with SQL <?xml version="1.0" encoding="utf-8"?> <DADX xmlns= xmlns:xsi= xmlns:xsd= > <operation name="listsales"> <documentation> Lists all the sales in the SALES table of the SAMPLE database </documentation> <query> <SQL_query>SELECT * FROM sales</sql_query> </query> </operation> <operation name="listdepartments"> <documentation> Lists all the departments in the DEPARTMENT table of the SAMPLE database </documentation> <query> <SQL_query>SELECT * FROM department</sql_query> </query> </operation> </DADX> 36 SQL calls are embedded in the DADX file. The action to be performed is defined using the SQL statements or DAD file references.these are used to retrieve the DB2 data and build the web service. It can also be used to call the XML extender functions. The XML extender uses WORF tools to implement web services. The DADX exposes the storexml and retrievexml operations as web services. 36

37 DADX calling a stored procedure <result_set_metadata name="listorg" rowname="org"> <column name="deptnumb" type="smallint" nullable="false"/> <column name="deptname" type="varchar" nullable="true"/> <column name="manager" type="smallint" nullable="true"/> <column name="division" type="varchar" nullable="true"/> <column name="location" type="varchar" nullable="true"/> </result_set_metadata> <operation name="listorg"> <documentation> Lists all the Organisations in the Org table of the SAMPLE database </documentation> <call> <SQL_call>CALL <username>.org()</sql_call> <result_set name="orgs" metadata="listorg"/> </call> </operation> Call to stored procedure 37 Stored procedures can also be called by web services. They can be invoked in the same way as an SQL statement. However with stored procedures, you need to consider result sets. Metadata must be explicitly defined in the DADX document. 37

38 Xquery Language used to query XML documents Based on XPATH specification Uses For Let Where Return (FLWR) expressions FOR specify set of tuples for the expression to be evaluated LET assigns a value to a variable WHERE discard particular tuples (filtering) RETURN defines what to return from the tuple Not currently supported in DB2 Have to use Xpath for limited query OR external XML query engines There should be further support for Xquery in future IBM development 38 Xquery is a flexible language used for extracting data from XML documents. Xquery is based on XPath specification and a lot of Xquery is incorporated in the current version of Xpath. The FLWR expressions can perform manipulation against the XML data. Xquery performs SQL like functionality against XML documents Xquery is not currently supported in DB2. However, IBM s intention is to have a database that handles both native XML data and relational data. 38

39 Xquery Xquery reads each document, parses it and manipulates it The output is an XML document Xquery is good for indexed document repositories It works best on hybrid documents containing narrative flow and quantified data If the document is pure data then it is better to transform it to relational data Xquery can access multiple documents in the same query Each document has to be loaded and parsed 39 The Xquery language will read each document, parse it and then manipulate it to project the data. The output will be an XML document. 39

40 Sample Xquery XML document <authorlist> <author name="david Owen"> <book>xml and DB2</book> <book>stinger enhancements</book> <book>high Performance UDFs</book> </author> <author name="joe Bloggs"> <book>db2 for Beginners, Vol. 1</book> <book>db2 for Beginners, Vol. 2</book> </author> </authorlist> XML query <most Authors> { let $indoc := document("authors.xml") for $author in ($indoc//author) let $cb := count($author/book) where ($cb >= 3) return <author>$author/@name</author> } </most Authors> <most Authors> <author>david Owen</author> </most Authors> 40 40

41 Xquery example <employee list> <employee empno=1234> <empname= Davies > <dept= A00 > </employee> <employee empno=3001> <empname= Jones > <dept= B01 > </employee> <employee empno=4001> <empname= Mullins > <dept= B01 > </employee> <employee empno=5001> <empname= Lewis > <dept= C02 > </employee> </employee list> Xquery <dept list> { let $indoc := document{ employeelist.xml } for $dept in distinct-values{$input//employee/dept/@name} return <dept name={$dept}> { for $employee in $input//customer where $customer/dept/@name =$product return <employee name={$employee/@name} /> } </dept> } </dept list>

42 Xquery <dept list> { let $indoc := document{ employeelist.xml } for $dept in distinct-values{$input//employee/dept/@name} return <dept name={$dept}> { for $employee in $input//customer where $customer/dept/@name =$product return <employee name={$employee/@name} /> } </dept> } </dept list>. <dept list> <dept number= A00 > <employee empno=1234> <emp name= Davies > </dept> <dept number= B01 > <employee empno=3001> <emp name= Jones > </employee> </dept> <dept number= B01 > <employee empno=4001> <emp name= Mullins > </employee> </dept> <dept number= C02 > <employee empno=5001> <emp name= Lewis > </employee> </dept> 42 42

43 XML Enhanced Support in DB2 UDB Session: H12 David Owen 43 43

44 Appendix A WITH l_temp(l_orderkey, l_xml) AS (SELECT l_orderkey, XMLELEMENT(NAME "lineitem", XMLELEMENT(NAME "l_orderkey", l_orderkey), XMLELEMENT(NAME "l_partkey", l_partkey), XMLELEMENT(NAME "l_suppkey", l_suppkey), XMLELEMENT(NAME "l_linenumber", l_linenumber), XMLELEMENT(NAME "l_quantity", l_quantity), XMLELEMENT(NAME "l_extendedprice", l_extendedprice), XMLELEMENT(NAME "l_discount", l_discount), XMLELEMENT(NAME "l_tax", l_tax), XMLELEMENT(NAME "l_returnflag", l_returnflag), XMLELEMENT(NAME "l_linestatus", l_linestatus), XMLELEMENT(NAME "l_shipdate", l_shipdate), XMLELEMENT(NAME "l_commitdate", l_commitdate), XMLELEMENT(NAME "l_receiptdate", l_receiptdate), XMLELEMENT(NAME "l_shipinstruct", l_shipinstruct), XMLELEMENT(NAME "l_shipmode", l_shipmode), XMLELEMENT(NAME "l_comment", l_comment) ) FROM tpcd.lineitem ), 44 44

45 Appendix A (continued) o_temp(o_orderkey,o_custkey, o_xml) AS (SELECT o_orderkey,o_custkey, XMLELEMENT(NAME "orders", XMLELEMENT(NAME "o_orderkey", o_orderkey), XMLELEMENT(NAME "o_custkey", o_custkey), XMLELEMENT(NAME "o_orderstatus", o_orderstatus), XMLELEMENT(NAME "o_totalprice", o_totalprice), XMLELEMENT(NAME "o_orderdate", o_orderdate), XMLELEMENT(NAME "o_orderpriority", o_orderpriority), XMLELEMENT(NAME "o_clerk", o_clerk), XMLELEMENT(NAME "o_shippriority", o_shippriority), XMLELEMENT(NAME "o_comment", o_comment), (SELECT XMLAGG(l_temp.l_xml) FROM l_temp WHERE l_temp.l_orderkey = o_orderkey) ) FROM tpcd.orders -- WHERE o_orderkey >= and o_orderkey < ) 45 45

46 Appendix A continued SELECT XML2CLOB( XMLELEMENT(NAME "customer", XMLELEMENT(NAME "c_custkey", c_custkey), XMLELEMENT(NAME "c_name", c_name), XMLELEMENT(NAME "c_address", c_address), XMLELEMENT(NAME "c_nationkey", c_nationkey), XMLELEMENT(NAME "c_phone", c_phone), XMLELEMENT(NAME "c_acctbal", c_acctbal), XMLELEMENT(NAME "c_mktsegment", c_mktsegment), XMLELEMENT(NAME "c_comment", c_comment), (SELECT XMLAGG(o_temp.o_xml) FROM o_temp WHERE o_temp.o_custkey = c_custkey) ) ) FROM tpcd.customer; 46 46