Working with XML data

DB2® pureXML® support lets you create tables, store and retrieve XML data in DB2 tables, and validate XML data.

Creation of tables with XML columns
To create tables with XML columns, you specify columns with the XML data type in the CREATE TABLE statement. A table can have one or more XML columns.
Altering tables with XML columns
To add XML columns to existing tables, you specify columns with the XML data type in the ALTER TABLE statement with the ADD COLUMN clause. A table can have one or more XML columns.
Storage structure for XML data
The storage structure for XML data is similar to the storage structure for LOB data.
Limitation of XML virtual storage usage
You can use the XMLVALA and XMLVALS subsystem parameters to limit the amount of DB2 virtual storage that is used for XML processing.
Insertion of rows with XML column values
To insert rows into a table that contains XML columns, you can use the SQL INSERT statement.
Updates of XML columns
To update entire documents in an XML column, you can use the SQL UPDATE statement. You can include a WHERE clause when you want to update specific rows. To update portions of XML documents, use the XMLMODIFY function with a basic XQuery updating expression.
Deletion of rows with XML documents from tables
To delete rows that contain XML documents, you can use the DELETE SQL statement. You can include a WHERE clause when you want to delete specific rows.
XML versions
Multiple versions of an XML document can coexist in an XML table. The existence of multiple versions of an XML document can lead to improved concurrency through lock avoidance. In addition, multiple versions can save real storage by avoiding a copy of the old values in the document into memory in some cases.
XML support in triggers
You can use the CREATE TRIGGER SQL statement to create BEFORE UPDATE or AFTER UPDATE triggers on XML columns. You can also use this statement to create INSERT or DELETE triggers on tables that include XML columns.
XML parsing
XML parsing is the process of converting XML data from its textual XML format to its hierarchical format.
XML schema validation
XML schema validation is the process of determining whether the structure, content, and data types of an XML document are valid according to an XML schema.
Casts between XML data types and SQL data types
Casting of SQL data types to XML data types occurs implicitly. The XMLCAST specification simplifies the task of converting an XML value to an SQL data type.
Retrieving XML data
You can retrieve entire XML documents from XML columns by using an SQL SELECT statement. Alternatively, you can use SQL with XML extensions (SQL/XML) to retrieve portions of documents.
Functions for constructing XML values
Several SQL/XML publishing functions can be used together to publish relational data in XML format.
Special character handling in SQL/XML publishing functions
The SQL/XML publishing functions make substitutions for some special characters when SQL values and identifiers are converted to XML values.
XML serialization
XML serialization is the process of converting XML data from its internal representation in a DB2 table to the textual XML format that it has in an application.
Differences in an XML document after storage and retrieval
When you store an XML document in a table and then retrieve that document, the retrieved document might not be the same as the original document.
Transforming an XML document with XSLTRANSFORM
The standard way to transform XML data into other formats is by Extensible Stylesheet Language Transformations (XSLT). You can use the XSLTRANSFORM function to convert XML documents into HTML, plain text, or different XML schemas.

Parent topic: Overview of pureXML