AN INTRODUCTION TO XQUERY seller nodes, description nodes,

AN INTRODUCTION TO XQUERY seller nodes, description nodes, and all others, we could change the path expression to the following. doc( data/test/items.xml )/items/itm/* Each evaluation step has an axis; in our simple query, we have let the axis default to child by leaving it out. The same query could be expressed this way. doc( data/test/items.xml )/child::items/child::itm/child::* Any other valid axis could also be used. Another common abbreviation is to abbreviate the attribute axis to @. The evaluation step /attribute:: status in a query against the document above could be abbreviated to /@status. Although XPath has much more functionality and a function library of its own (that can be used in path expressions in XQuery) in addition to being able to use the XPath and XQuery operators and functions, we ll finish by discussing XPath predicates. After you filter any evaluation step by using a node test, you can filter the results further by using a query predicate. Query predicates follow the node test in square brackets. For example, this predicate filters itm elements whose itemno subelement has a text subelement with a value less than 1000. doc( data/test/items.xml )/items/itm[itemno/text() < 1000] A predicate can be as simple or complex as you want, but it must evaluate to a boolean value. More exactly, it is evaluated using the Effective Boolean Value (essentially, the rules for fn:boolean) for example, /a[1]. You can even have multiple predicates on the same evaluation step if you want. The heart of XQuery expressions, what forms most of the selection logic in an XQuery query, is called the FLWOR expressions. FLWOR is an acronym for the five main expression keywords: for, let, where, order by, and return. We ve already seen the letexpression, to assign a value to a variable, and the returnexpression, for returning the value of a variable in the query. let $a := doc( data/test/items.xml ) return $a We ll briefly define the use of each expression. Note: If you are looking for good and high quality web space to host and run your application check Lunarwebhost Tomcat Web Hosting services

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