XQuery from the Experts: A Guide to the W3C XML Query Language

LOB or Compose?

The most basic dichotomy in mapping between XML and relational data is the choice between representing an XML document in a single column or in multiple columns: LOB representation or composed representation. Additionally, relational databases that have been extended to add XML functionality may implement a native XML type.

In an LOB representation, a column in a database table contains a literal XML string, usually in a CLOB (character large object) or similar datatype—hence the name. A single application might store multiple types of XML documents in different columns or even in the same column. Listing 6.1 shows an example of LOB XML. In this example, we have a database table that stores purchase orders as XML documents in ...