Most web applications have connections to databases and use XML to transfer data from the database to the webapplication and vice versa. Every major database vendor has proprietary extensions for using XML with relationaldatabases, but they take completely different approaches, and there is no interoperability between them. Manydevelopers need to be able to write applications that work for databases from multiple vendors. XQuery [XQuery] and SQL/XML [SQL/XML] are two standards that use declarative, portable queries to return XML by querying data. In both standards, the XML can have any desired structure, and the queries can be arbit-rarily complex. XQuery is XML-centric, while SQL/XML is SQL-centric. SQL/XML is an extension of SQL that is part of ANSI/ISO SQL 2003. It lets SQL queries create XML structureswith a few powerful XML publishing functions. For a SQL programmer, SQL/XML easy to learn because it involvesonly a few small additions to the existing SQL language. Since SQL is a mature language, there are a lot of toolsand infrastructure for SQL. For instance, SQL/XML uses JDBC to return results, and there is currently no equivalentstandard API for XQuery. SQL also has functionality not yet found in XQuery, such as updates or stored procedures.