Extending XQuery for Grouping, Duplicate Elimination, and Outer Joins
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Borkar, Vinayak and Michael Carey
IDEAlliance
2004

Abstract:

XQuery is the W3C’s emerging language standard for querying and transforming XML. XQuery is a powerful, flexible language designed to query the many kinds of structured and unstructured data that XML can represent. Despite its power, certain familiar SQL query operations, such as grouping, duplicate elimination, and outer-joins, are either difficult or impossible to express “reasonably” in XQuery. These primitives are important for data-oriented applications of XML, particularly applications that have a need for reporting (e.g., for OLAP and statistical querying). This paper presents a small set of XQuery extensions to enable grouping, duplicate elimination, and outer-join queries all to be expressed neatly within the XQuery language. The proposal does minimal “damage” to the XQuery standard; it generalizes the current FLWOR expression syntax of XQuery and requires no changes to the underlying XQuery data model. The extensions are slated to appear in the next major revision of the BEA XQuery engine and its encompassing products.