Information Modeling and Relational Databases, 2nd Edition

13.9. Exploiting XML

SQL/XML

SQL:2003 introduced XML as a new built-in data type. XML data is strongly typed: XML values are assumed to be tree-like data structures that are distinct from their representation in the form of a text string. The XML type can be used wherever other SQL types are allowed: in table columns, as parameters of a routine, as variables, and so on. Although relational data and XML data are both structured, there are some significant differences between them. The Table 13.5 identifies a few distinctive points.

XML data can be stored in a database either in a text column (i.e., char, varchar, or dob) or in a column of data type xml. A textual representation might be preferred if it is important to retain the textual fidelity ...