The general FLWOR structure
The peculiarity of XQuery in comparison to simple path expressions as being introduced in XPath 1.0 is that XML documents are no longer filtered with regard to an indicated criterion, but can be transformed in any way and in doing so, new XML documents can be generated which do not have to be related to the source documents.
The central main construct for the formulation of new XML documents with the help of XQuery is the concept of the FLWOR expressions which is closely examined on the following pages. FLWOR expressions enable the binding of variables, the iteration over node sets of referenced XML documents and the indication of "templates" for the structure of the result documents.
The "Hochwaldklinik.xml" file serves as universal example scenario for the explanation of the introduced constructs. As discourse area the administration of a hospital ("Hochwaldklinik") with all its institutions, employees and patients is (radically simplified) illustrated.
- FLWOR expressions
- Let and For clause
- Binding of several variables
- Explicit type testing
- Where clause
- Order-by clause
- Cancellation of the sorting
- Return clause
- Nesting of FLWOR expressions
- Bracketing in the Return clause
Source: "XQuery – Grundlagen und fortgeschrittene Methoden", dpunkt-Verlag, Heidelberg (2004)
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