Download XML and DB2

XML and DB2
By Josephine Cheng, Jane Xu
IBM Santa Teresa Laboratory
Slides edited from the original slides of Yunyu Song
Outline
 Net.Data
 XML Extender
 Create XML document from DB2
 Transform XML document to DB2
 Searching XML documents
 Conclusion
Net.Data VI
 A scripting language to create web
applications which can access data from
any ODBC compliant databases (e.g.
DB2, Oracle, DRDA, ODBC, flat files and
web registry data)
 Can generate XML documents from SQL
queries.
 Its successor product is WebSphere
Application server.
Generating XML documents from
existing DB2 data
 Net.Data Macro to generate XML Data
Generating XML documents from
existing DB2 data
 Resultset of XML data generated by
Net.Data
Outline
 Net.Data
 XML Extender
 Create XML document from DB2
 Transform XML document to DB2
 Searching XML documents
 Conclusion
XML Extender
 Repository for XML documents and their
DTDs.
 Data management functionalities (integrity,
security, recoverability and management).
 User has the option to store the entire
document as an column or decomposed
into multiple tables and columns.
 Users can retrieve the entire document or
extract XML elements and attributes
dynamically in an SQL query.
XML Collection
 SQL Collection Mapping
It only works when you can collect all relevant data with a single SELECT statement,
which is placed in the DAD. If multiple tables are involved you should use primaryforeign key relationships.
 RDB_Node Collection Mapping
It allows node definitions for multiple tables. All involved tables must have primary
keys. This approach does not require SQL in the DAD. It does allow imports as well
as exports.
XML Collection
XML Collection
XML Column
 Store entire XML document in a column of




XML type
Allows to query XML content
Associate and store DTD in DB2 for one or
more document
Map element and attribute to DB2 table (side
table)
Used when your XML storage is mainly
archival or for reference, and document
content is updated infrequently
XML Column
XML Column
DAD File
 Define which DB2 tables hold the data
 The mapping method: SQL Collection, RDB
Node Collection, or XML Column
 Whether to validate XML documents with a DTD
before storing or translating the contents
 Which DTD to use for validation and translation
Sample DAD (SQL Collection)
Sample DAD (RDB Node Collection)
Sample DAD (XMLColumn)
XML in DB2
Outline
 Net.Data
 XML Extender
 Create XML document from DB2
 Transform XML document to DB2
 Searching XML documents
 Conclusion
Create XML from DB2
 Generate XML fragments (SQL Collection)
 Generate whole XML documents (RDB
Node Collection)
Generate XML fragments (SQL
Collection)
REC2XML
Return XML fragments
XMLELEMENT
Return Single elements
XMLATTRIBUTES
Group elements as XML
attributes
XMLAGG
Aggregate elements in a
hierarchy
Examples I
SELECT XML2CLOB( XMLELEMENT(NAME "Department",
XMLATTRIBUTES(e.workdept AS "name"),
XMLAGG(XMLELEMENT(NAME "emp", e.lastname) ORDER BY
e.lastname) )) AS "dept_list" FROM employee e WHERE e.workdept IN
('C01','E21') GROUP BY workdept
This query produces the following output.
dept_list
<Department name = "C01">
<emp>KWAN</emp>
<emp>NICHOLLS</emp>
<emp>QUINTANA</emp>
</Department>
<Department name = "E21">
<emp>GOUNOT</emp>
<emp>LEE</emp>
<emp>MEHTA</emp>
<emp>SPENSER</emp>
</Department>
Example II
 REC2XML Fuction
select rec2xml(1.0, 'COLATTVAL','MyRow',DEPTNO, DEPTNAME,
MGRNO) AS MYROWS FROM DEPARTMENT
MYROWS
-------------------------------------------------------------------<MyRow>
<column name="DEPTNO">A00</column>
<column name="DEPTNAME">SPIFFY COMPUTER SERVICE DIV.</column>
<column name="MGRNO">000010</column>
</MyRow>
<MyRow>
<column name="DEPTNO">B01</column>
<column name="DEPTNAME">PLANNING</column>
<column name="MGRNO">000020</column>
</MyRow>
Compose XML documents
(RDB Node)
dxxGenXML
dxxGenXMLClob
generates an XML document according to the given
DAD and places the result in a table you specify
used when document update occasionally
identical with
dxxGenXML
except that it returns the XML directly as a Character
Large Object (CLOB)
dxxRetrieveXML
Used when composing or decomposing XML
documents frequently
Using the dxxEnableCollection stored procedure to
create a named collection and stores the DAD within
the database
Then refer to it by name using dxxRetrieveXML and
dxxRetrieveXMLClob
Examples
dxxGenXML(CLOB(100K) DAD, /* input */
char(resultTabName) resultTabName, /* input */
integer overrideType /* input */
varchar(1024) override, /* input */
integer maxRows, /* input */
integer numRows, /* output */
long returnCode, /* output */
varchar(1024) returnMsg) /* output */
dxxRetrieveXML(char(collectionName) collectionName, /* input */
char(resultTabName) resultTabName, /* input */
integer overrideType, /* input */
varchar_value override, /* input */
integer maxRows, /* input */
integer numRows, /* output */
long returnCode, /* output */
varchar(1024) returnMsg) /* output */
Outline
 Net.Data
 XML Extender
 Create XML document from DB2
 Transform XML document to DB2
 Searching XML documents
 Conclusion
Transform XML into DB2
 XML RDB_Node Collection
 XML column
RDB_Node collection
 In this case it is the reverse of generating XML from an RDB Node
Collection.
The end result of this is pure relational data, in tables, and ready to be
accessed with the usual database tools. You can do Queries, indexes,
views, optimizations etc.
 dxxShredXML
Takes the DAD as a parameter, similar to dxxGenXML
Used for applications that do occasional updates
 dxxInsertXML
Uses a DAD already stored, similar to dxxRetrieveXML
Used for applications that make regular updates
Takes an enabled XML collection as input parameter
UDTs provided by XML extender
(XML Column)
XMLCLOB
XML content stored as a character
larger object (CLOB) in DB2
XMLVARCHAR
XML content stored as VARCHAR in
DB2
XMLDBCLOB
XML document stored as double
byte CLOB in DB2
XMLFILE
XML document in a file on a local
file system
Store XML as XML Column in
DB2
1. Ensure that the database is XML-enabled
2.
3.
4.
5.
6.
7.
Optional: Locate or create a DTD for your documents and store it
in DB2XML.DTD_REF.
Create the table to store the XML documents and add the XML
column. Also create any side tables.
Create a DAD to map the XML to the relational DB structures.
Enable the XML column, specifying the DAD.
Create indexes for the side-tables.
Insert some XML documents and start performing queries.
Key Features of XML Column I
 The XML extender supports a subset of XPath, providing
a way to locate specific data within an XML document.
 Combined with the provided extracttype functions
(extractInteger, extractTimestamp, extractVarChar, etc.)
you can retrieve values as database types.
Example I
Example II
Key features of XML Column II
 You can select to copy specific element and attribute
values to a side table. Doing that lets you search and
manipulate the values directly via SQL just like any other
column data, linking to the stored XML to pick up related
values.
 You can create side table indexes, to improve search
time.
Use side table for fast search
Key features of XML Column III
 XPath based element or attribute update
UPDATE sales_tab SET order = Update(order,
'/Order/Customer/Name', 'Customer X') WHERE sales_person =
'Salesperson Y'
Using the Update function, you can correctly alters both the stored
XML document and any relevant side tables.
Outline
 Net.Data
 XML Extender
 Create XML document from DB2
 Transform XML document to DB2
 Searching XML documents
 Conclusion
Searching XML docs (XML Column)
 Example
of
XML
Column
Searching XML documents
(Column)
 Using side tables.
 Can make a view of the joint.
Searching XML documents
(Column)
 Example of query against attribute.
 The UDF is expensive. Alternatives:
 Use DAD to define CUSTOMER as another index in
the side table.
 Enable XML column to use text indexing (e.g. section
search with db2tx.contains).
Searching XML documents
(Collect)
 Search can be done directly against the
SQL based tables, or using procedures
dxxGenXML() and dxxRetrieveXML().
 The DAD is used to specify whether to
retrieve the entire document or a fragment.
 The DAD is also used to specify the
search criteria which can be based either
on tables or SQL query.
Outline
 Net.Data
 XML Extender
 Create XML document from DB2
 Transform XML document to DB2
 Searching XML documents
 Conclusion
Conclusion: XML in DB2
Requirement
Solutions
generate XML document from
relational data (DB2 tables)
Use simple functions (REC2XML XMLELEMENT etc.)
Use a "SQL Collection" to map a query to an XML document
structure
Use an "RDB Node Collection" to map a number of tables to an
XML document structure (this also allows XML import)
Use Net.Data Macro to generate XML Data
Ignore DB2's capability and use Visual Basic or VB Script
Transform XML to relational data
Use “RDB_node collection” to store XML in DB2 tables
Store XML documents in DB2
Database for later reference
Use an "XML Column" to store entire XML documents.They can still
be indexed and queried via DB2 functions