FLWOR

The programming language XQuery defines FLWOR (pronounced as 'flower') as an expression that supports iteration and binding of variables to intermediate results. FLWOR is an acronym standing for FOR, LET, WHERE, ORDER BY, RETURN. FLWOR is loosely analogous to SQL's SELECT-FROM-WHERE and can be used to provide join-like functionality to XML documents.

*"for" creates a sequence of tuples
*"let" binds a sequence to a variable
*"where" filters the tuples on a boolean expression
*"order by" sorts the tuples
*"return" gets evaluated once for every tuple

Example

for $d in doc("depts.xml")//deptno let $e := doc("emps.xml")//employee [deptno = $d] where count($e) >= 10 order by avg($e/salary) descending return { $d, {count($e)}, {avg($e/salary)} }

External links

* [http://www.w3.org/TR/xquery/#id-flwor-expressions W3C XML Query (XQuery) - FLWOR Expressions]
* [http://www.brics.dk/~amoeller/XML/querying/flwrexp.html FLWOR examples]
* [http://www.stylusstudio.com/xquery_flwor.html Introduction to FLWOR]