An update statement may occur at any position within the XQuery main code or a function body.When using an update within the return clause of a FLWOR expression, it should be clear that one should not delete or replace nodes that are still being used by enclosing code.This module is created to provide an optimized way to perform operations on XML in memory.
We thus provide an extension to XQuery, which maps each of the XUpdate instructions to a corresponding XQuery expression.Until the W3C working group starts its work on an official update specification, the basic syntax follows the proposal by Patrick Lehti. However, it is not suitable for updating temporary document fragments constructed within the XQuery, i.e.I’ve never been one of those geeks who cares too deeply about execution plans as long as my queries run reasonably quickly. ” But this quirk does have two major impacts on XQUF. The second consequence of this XQUF quirk is that you cannot, therefore, query XQUF changes in the same command in which you are making them.Firstly, it means that your XQUF operations can be written in pretty much any order you like, which is nice. And that’s because those changes are not executed until the end of that command.Previous versions of e Xist already offered some functions to execute XUpdate queries from within XQuery.
However, this approach had its limitations, mainly due to the lack of integration between the XUpdate language and XQuery.XQuery, a powerful scripting language used specifically to access XML data, contains the elements necessary to create complex expressions that can include functions, operators, variables, and values.MSDN provides a complete XQuery language reference that you can refer to while you work with the method might also require a Transact-SQL data type as a second argument or a table and column alias tagged on after the arguments.The XML Data type has definite uses, but the way of interrogating, retrieving, and manipulating the values of properties and attributes within XML have been so foreign to the SQL language as to be somewhat of a barrier to their use.Fortunately, Robert Sheldon has once more managed to make the subject accessible to those of us who just need to get the job done. Based on those examples, it might seem that retrieving XML data is similar to retrieving objects configured with other data types.And so, in 2009, the XQuery Update Facility – a small extension to XQuery – became a W3C Candidate Recommendation, and, by 12c it had found its way into Oracle (we need to talk in detail about Oracle’s implementation of XQuery Update Facility, but we’ll do that a little later). “XQuery Update Facility” is far too much typing, and so it is often abbreviated to XQUF, which looks less like a name and more like a toddler closing his eyes and banging wildly at a keyboard. And before we dive head first into XQUF and its syntax, we should mention a few of its quirks.