# XML data types and operators

Derby supports the XML data type and a set of operators that work with the XML data type, but does not provide JDBC support for the XML data type. The XML data type and operators are based on a small subset of the SQL/XML specification.

The XML data type and operators are defined only in the SQL layer.

There is no JDBC-side support for XML data types. It is not possible to bind directly into an XML value or to retrieve an XML value directly from a result set. Instead, you must bind and retrieve the XML data as Java strings or character streams by explicitly specifying the appropriate XML operator as part of the SQL statements:

- Create a table with a XML data typed column. For example:

      CREATE TABLE xml_data(xml_col XML);

- Use the XMLPARSE operator for binding data into XML values. For example:

      INSERT INTO xml_data(xml_col)
        VALUES(XMLPARSE(DOCUMENT ' <name> Derby </name>' PRESERVE WHITESPACE));

  Note: You must insert the XML keywords DOCUMENT and PRESERVE WHITESPACE. Actual XML data should be inside single quotation marks, and values should be within the starting XML tag and the ending XML tag.
- Use the XMLSERIALIZE operator to retrieve XML values from a result set. For example:

      SELECT XMLSERIALIZE(xml_col AS CLOB) FROM xml_data;

  Note: You can also specify `xml_col AS VARCHAR(25)`.
- Use non-XML data retrieved from a non-XML column to create an XML fragment. For example:

           SELECT '<my_self>' ||
           '<name>'|| my_name ||'</name>' ||
           '<age>'|| TRIM(CHAR(my_age)) ||'</age>'||
           '</my_self>'
           FROM my_non_xml_table;

  Note: This will result in XML fragments, which you must plug into an XML document.

Additionally, there is no JDBC metadata support for the XML data type.

The XML data type is not allowed in any of the clauses or operations that are described in the section on expressions on LONG data types in Derby and standards.

For the XML operators to work properly, Derby requires that the Java Virtual Machine (JVM) have working implementations of the javax.xml.parsers.DocumentBuilderFactory and javax.xml.xpath.XPathFactory classes. All supported JVMs implement these classes.

Parent topic: Derby and standards