XQuery

To a large degree, the return sequence of an XQuery function depends exclusively on the parameters with which you call it.

The XML Query Working Group did not draw up a formal list of the principles that guided the design of XQuery.

While XQuery was designed for querying large document bases, it serves as a fine tool for transforming simple documents as well.

I talked to several database vendors on the exhibit floor and attended several more XQuery presentations to try to make some sense of this.

FLWOR ( "flower" ) is often mentioned in the context of XQuery.

XQuery uses a concise set of commands to make it easy to work with XML data.

Additionally, the existential nature of the XQuery general comparison predicates requires attention when you express a "between" condition.

It is often used outside of any relational databases to query XML data, which may be stored in text files.

For advanced XML users, XQuery can be very helpful in querying and extracting content out of large XML documents.

For the moment, most native XML databases fill this hole in various, proprietary ways, often implemented as an XQuery extension.

This fluidity makes XQuery just as appropriate as a database search system as it is to queue filtering.

From a development costs perspective, the XQuery approach turned out to be a significant savings.

Plain XQuery does not allow you to call SQL user defined functions (UDFs) or external UDFs written in C or Java.

The next example filters the set of input documents to XQuery by joining with a nickname.

An XPath statement in an XQuery or XSLT stylesheet might test for one of the predefined elements and also display the known color.

XQuery allows a client to describe precisely the type of XML document that it would like the server to return.

As you might imagine, the XQuery where clause enables you to filter results based on the value of the zip element in your XML documents.

At the end of this tutorial, you will have a working example of an XQuery function and its applicability to a business requirement.

Added to the list of requirements for a view that direct references to Xquery expressions are not allowed in an indexed view definition.

Using SQL group by and aggregation functions on that table is usually more efficient than producing the same result in plain XQuery.

For each purchase order an XQuery is executed that returns a formatted result of each product subtotal.

XQuery is good for XML-only applications that do not need (or do not wish) to use SQL or relational structures.

XQuery looks like SQL and solves many of the SQL problems that cause me to run back to my bookshelf for answers.

Depending on the XQuery implementation, this construction may be inefficient in terms of memory consumption.

I'll show you a few quick XQuery expressions to give you a flavor of what XQuery can do, and then move on to the screen-scraping examples.

The transform expression is at the core of the XQuery Update Facility, an emerging standard to extend XQuery to modify XML documents.

The tutorial ends with a section on mixing XQuery and SQL and combining the power of the two languages.

One of the language syntax requirements for XQuery is that the Query language MUST be convenient for humans to read and write.

XML Query, often abbreviated as XQuery, is a specification that's been around in one form or another for a few years now.

IBM provides XQuery functions that allow you to query relational data and mix and match the results with the XML from the XML-aware columns.

XQuery implementations usually deliver both the XQuery scripting capability and a data persistence or storage facility.

Instead, you write an XQuery that transforms your existing response data into a RosettaNet response.

As such, it is a good option if your applications require querying and manipulating XML data only, and do not involve any relational data.

It is possible to create views on XML that apply XQuery update to hide or restructure portions of XML.

SQL embedded in XQuery also allows you to run external functions on the XML columns.

The XQuery modules feature allows you to group commonly used functions and variables in reusable library modules.

One of the main benefits of XQuery over other formats is that you can contain the processing and XML within the same file.

Less mature than XSLT as a specification, XQuery may become the SQL of the next decade.

Using XQuery, it takes only a few lines of code to retrieve valuable information from your Maven POM files.

The Saxon XQuery engine was used to compile and execute the query against the DOM object of the document.

A feature of XQuery is its ability to indicate a specific document to which you can apply a query.

I expect the SQL-style approach will wind up in the XQuery specification.

The view can be queried with SQL statements and embedded XQuery, as shown in the following example.

Casting to a string or untypedAtomic type transforms the value to its XQuery canonical lexical representation.

XQuery greatly enhances UDDI solutions as it better manages and governs the resources listed in a UDDI registry.

My interest in XQuery comes from its implementation as a native XML environment for application development.

With information specified as an XML document, you can retrieve data with an XML query language, like XQuery.

To achieve this, the XMLQUERY function allows you to embed any XQuery expression in an SQL statement.

The XQuery data model supports any general type of document and any general dynamic parameter used to fetch and construct the document.

As you type SQL and XQuery statements in the editor, the syntax in the statements is validated.

If the local store is an XML database, the XQuery processing might be even faster because of the indices in the database.

XQJ is a generic XQuery data access framework, which provides a uniform interface on top of a variety of different XQuery implementations.

XQuery is a language for fetching data similar to SQL, but it has more sophisticated data manipulation constructs.

Any path in an SVG file can be located by parsing the XML or using advanced techniques like XQuery or XPath.

The purpose of this chapter is to discuss the major influences on the design of the XQuery language.

XQuery uses XPath expression syntax to address specific parts of an XML document.

Fields of a relational database resulted in poor query performance when an XQuery engine was simply layered on top.

XQuery uses a simple syntax that is a mix of XML, XPath, comments, functions, and a special expression syntax to tie it all together.

You need to run Listing 7 in an instance of the eXist XML database loaded as an XQuery file.

Also, because XQuery is a functional programming language, each function stands on its own.

Unlike a traditional Web application framework, XQuery can construct the business logic easily in a query file.

Its auto-code complete features enable you to create XQuery documents easily.

On close inspection of this query, only a single character differs from the XQuery shown earlier.

The "let" statement is itself composed of a FLWOR (for, let, where, order by, and return) XQuery expression.

Although grouping and aggregation can be expressed in XQuery using self-joins, it is quite awkward.

However, the return clause of XQuery enables you to transform XML output as needed.

You can import any number of library modules into the main XQuery module that contains the XQuery body.

With some effort, data does not even need to be in XML format to be processed using XQuery.

Lots of other implementations of XQuery are available, some free, some commercial -- see Resources for some places to look.

XML and XQuery are emerging standards with an increasing adoption in information management.

The same query can be formulated using FLWOR expressions commonly associated with XQuery statements.

Data type forms the input XQuery data model on which the XQuery expressions are executed.

XQuery clearly outperforms publishing queries when complex data must be retrieved.

As with the basic changes, each query has its specification, the equivalent XQuery statement, and its result.

You can check this output using any of a number of XQuery clients.

Note that XQUERY, by default, serializes its result set into a CLOB.

Given that XPath and XQuery are already used within the XML database for navigation and query, these skills are likely already known.

The listings that follow describe each display area and explain the main principles of what XQuery does.

Both SQL and XQuery can be combined in a single statement to restrict searches for both XML and non-XML columns.

This game was developed to help you use the skills built with the " SQL and XQuery tutorial for IBM DB2" tutorial series.

It is a waste not to use XQuery outside of native XML databases, as well.

We also just got a code contribution to support XQuery, that's another candidate proposal for the spec.

Further, some XQuery expressions are repeated within a variety of processing routines.

XQuery functions are strongly typed, support recursion, and can be declared as internal or external.

Using XQuery to query against and transform an XML model is an excellent way to make that happen in a contemporary Web application.

You specify XQuery against an xml type column or variable by using one of the XML Data Type Methods.

Listing 4 shows an even simpler XQuery expression, which outputs the number of distinct publishers in the bibliography in a single element.

Indeed, most XQuery implementations have extended beyond the XQuery standard to enable XQuery to make SOAP requests.

The service uses XQuery to determine if the cache is valid based on a query to the metadata description of the service request.

This topic provides XQuery examples against XML instances that are stored in various xml type columns in the AdventureWorks database.

The service uses XQuery to determine if the cache is valid based on a query to the metadata description of the service request.

This topic provides XQuery examples against XML instances that are stored in various xml type columns in the AdventureWorks database.

Most native XML databases provide XQuery extensions that are designed to run fast.

The real reason that businesses fail to take advantage of the full power of XQuery is fear of the unknown.

Just like SQL is a query language designed for the relational data model, XQuery is a language designed specifically to query XML data.

Outside XML databases, you can use command-line programs or write a few lines of Java code to invoke XQuery.

XQuery, the language that can be used to query XML documents, has added extensions to perform sub-document updates on XML documents.

You can then use XQuery, SQL, or any of the application development interfaces that DB2 offers, to access and manipulate the XML data.

For this sample dashboard, I use publicly available data to illustrate how XQuery handles integration scenarios.

However, some implementers and existing implementations offer a more free-form way of composing an update with XQuery.

However, some implementers and existing implementations offer a more free-form way of composing an update with XQuery.

This compares more to a sub-select within an SQL where clause, but the XQuery syntax seems more intuitive and natural.

2006 was no exception: XQuery still didn't arrive in force or even get to a finished specification.

The XQuery that creates the details information for the product is saved as a stored procedure.

When it's sensible to begin using XQuery really depends on when you're reading this column and how eager you are to start using a new spec.

Many person-years have been spent in defining XQuery, and many more will be spent on its implementation.

Like previous examples, we want to return a valid XML document, so we will wrap the result of the XQuery with the root XML element.

The XML Data Modification Language (XML DML) is an extension of the XQuery language.

XQuery, at its simplest, is a language used to define searches of XML documents.

A standard FileReader object is instantiated with the location (as a string) of the XQuery file in the constructor.

A standard FileReader object is instantiated with the location (as a string) of the XQuery file in the constructor.

Scalability and performance of XQuery solutions depend on the target of the XQuery implementation.

Listing 15 shows how XQuery update can be used to produce the novation response or confirmation.

The XQuery is sent as the value of the _query field in the URL's query string (the part of the URL after a question mark).

The FpML XQuery update example in this article (see Figure 6) illustrates producing a response to a novation request (see Resources).

XQuery is a solution that enables your business to migrate to the new standard without stopping your existing sales operation.

Note that both document and unparsed-text are in the XSLT function set, not the "fn: " F&O set, and are not available for XQuery and XForms.

To software architects and developers, XQuery delivers increased productivity and agility.

In particular, you can use relational predicates to restrict the input to a particular XQuery.

Note that you should carefully check the performance of the access through the XQuery update views.

Note that you should carefully check the performance of the access through the XQuery update views.

Now that SQL has helped obtain a subset of XML documents, the XQuery uses a let binding to a variable $total.

Database companies see XQuery as an opportunity to augment their core solutions.

In XQuery, the code relies on XPaths to point directly to the interesting elements and loops must be written explicitly.

Employing non-unique element names can hinder your ability to evaluate or profile some XQuery or XPath alternatives for locating your data.

XOP is a means of more efficiently serializing XML Infosets that have certain types of XQuery and XPath 2. 0 element content.

Finally, XQuery works best on "hybrid" documents -- documents that contain both narrative flow and quantified data.

XQuery implementations exist for most available programming languages.

An equally important benefit to the XQuery processor is the ability to define policies that operate on the data at runtime in the mid-tier.

Finally, the main web page examines the master file, extracts the data using XQuery, and renders the final display.

Finally, the main web page examines the master file, extracts the data using XQuery, and renders the final display.

XQuery, on the other hand, allows you to sort the results or transform them into HTML, CSV, SQL, or any other text-based format.

In which it takes XML tto be the unified view, takes the overall situation query language with XQuery .

The XQuery where clause contains the join condition, comparing the manager names with the employee name elements.

You cannot write business logic in XQuery because XQuery focuses exclusively on querying and transformation.

These problems require the programmer to move beyond XPath to a tool like XQuery.

New query language support (for XQuery), a new graphical query builder (for XQuery), and new query optimization techniques.

XMLTABLE is a SQL table function that returns a table from the evaluation of XQuery expressions on an XML document.

The code in Listing 6 creates an XQuery expression that reaches out to the required element.

That index cannot be used in Query 8 because the join condition is not a relational predicate but an XQuery predicate.

Programmers can now search for data using SQL or XQuery, a new query language that supports navigational (or path-based) expressions.

The XQuery body is made up of a sequence of expressions that specify the intended query result.

The XQuery documentation refers to the transform process as a query but the meaning is the same.

The parameter marker is passed as a variable ($z) into the XQuery expression.

The SQL view definition is read-only and must be manipulated with embedded XQuery.

Users can retrieve entire XML documents or document fragments by incorporating XPath, XQuery, and SQL into queries.

XQuery as the view used in conjunction with XML as the data represents an even better way to split the concerns.

Note that you only need to do this if you are using XQuery as the outermost (or top level) language.

This sample grammar is extremely small and does no justice to the richness of expression and data types supported by XQuery.

XQuery provides a better user experience by reducing the size of content transmitted over the network.

I predict XQuery will become a very important example of the latter.

The spec (being led by Oracle) aims to provide standard programmatic access for XQuery implementations in Java.

FastSOA is an architecture that provides a mid-tier service binding, XQuery processor, and native XML database.

But what happens in the case of XQUERY and SQL together in the same request?

A path expression in XQuery consists of a series of steps, separated by slash characters.

Listing 11 also demonstrates Zorba's support for the XQuery where clause, which is commonly used to filter the output result set.

Each email is stored internally as an XML document and accessed using XQuery.

Like SQL, XQuery contains functions for extracting, summarizing, aggregating, and joining data from multiple datasets.

Note that the XQuery is specified against the Instructions column of xml type.

XQuery is a World Wide Web Consortium (W3C) standard designed specifically for extracting information from XML documentation.

The two need not be mutually exclusive, and indeed some repositories that implement XAPI also implement XQuery.

The XQuery prolog is a series of declarations and definitions that together create the required environment for query processing.

The application simply sends an SQL UPDATE statement with an embedded XQuery transform expression to the DB2 server ( Figure 2).

This first part of the article shows how you can use pure XQuery to start classifying content.

However, XQuery column names are represented with a number.

You do exactly the same thing in terms of calling the web service from XQuery, as Listing 13 shows.

is a good hub resource for XQuery, and includes a Wiki, a collaborative resource index and discussion page.

It is true that the XQuery specification does not include an update mechanism.

The following statement executes an XQuery expression and return values as a table from the DATA column.

This expression is part of the emerging XQuery standard for updating XML data.

A remarkably small amount of code is needed to execute XQuery expressions against HTML pages.

The global path index results in improved storage efficiency and minimizes the path look-up time for XQuery execution.

The XQuery is executed against the XML instance identified in the query generating the XML.

All optimization guidelines are also applicable to queries written in the XQuery language.

Further XQuery information indicates that DB2 should only return the "Message" portions of such comments.

The database vendor that delivers fast performance and XQuery flexibility first will win a huge new market.

XQuery bridges these data warehouses by showing which products cause the most unresolved support calls.

Two possibilities immediately sprang to mind; HSQLDB, the open-source in-memory SQL database, and XQuery.

The goal of this tutorial is to give you a practical grounding in how to develop applications with XQuery.

For more information about XML construction, see XML Construction (XQuery).

This information is extracted from the actual XML models by table extractor functions or by XQuery queries.

Or you could use Zorba, a stand-alone XQuery application, to do the same thing.

The XML returned by XQuery is inserted without a wrapping element.

The ability to specify an XQuery query against XML data stored in columns and variables of the.

XQuery offers a solution to assist OLAP by providing a query-based link between multiple data warehouses.

This chapter is based on the most recent XQuery specification at the time of publication.

I also often hear the claim that while XQuery syntax looks nicer, it lacks XSLT's template style pattern matching.

It also supports the XQuery language, including the XML Data Manipulation Language (XML DML).

A powerful aspect of XQuery is its ability to transform XML output from one form of XML into another.

While this is an XML oriented design XQuery and native XML databases handle non-XML data, including images, binary files, and attachments.

The data. xq XQuery file's job is to generate an XML document containing all KPI-related data.

XQuery is pretty much a complete programming language, constituting a superset of XPath.

Others are stand-alone XQuery processors not tied to a database.

In the following example, an XQuery constructs a result document that contains the book, inventory and information for a specific book.

If you wanted the query to return an HTML fragment representing the result as a numbered list, you can apply the XQuery from Listing 6.

Other less familiar query languages include Object Query Language (OQL) and XQuery.

Describes a list of the XQuery functions that are supported.

XQuery benefits developers by reducing the amount of code needed to perform a query.

In Listing 4, the result returned from the XQuery code is annotated as an XML fragment with data returned from the query.

They also assumed that you worked with typed data, such as a database extract, and XQuery is a strongly typed language.

As indicated in Query 19, XQuery with embedded SQL can be useful to feed relational data into an XQuery.

Although DB2 fully supports XQuery as a top-level language, the initial XQuery specification didn't address parameter markers.

Where you ll find links to various XQuery specifications and implementations.

You can specify XQuery against the XML data stored in a column or a variable of xml data type.

XQuery defines several optional features, which are described in this section.

These functions allow users to embed XQuery or simple XPath expressions in SQL statements.

Looking forward to 2007, I think XQuery and native XML databases will be very, very hot.

One of XQuery's little-used, but most important features is its ability to indicate the document to apply an XPath to.

Querying using XQuery on a XML column of an indexed table.

Generality: XQuery is intended for use in many different environments and with many kinds of input documents.

Furthermore, the update part of XQuery is marching forward rapidly.

However, sometimes XQuery is easier to use, even when working with relational data.

Develop your SQL statement, stored procedure, or XQuery statement.

In our sample implementation, we have created the Web service using PHP and XQuery to do price and tax calculations.

Describes XQuery operators that are supported.

XQuery uses the terms namespace prefix and namespace URI when discussing its syntax.

The value produced by that XQuery is either the customer's name element if the predicate is true, or the empty sequence otherwise.

Your basic system is in place to output a single RSS feed as HTML by using XQuery. Now you need to handle multiple feeds.

XQuery is a query language that uses the structure of XML intelligently to express queries across many types of XML data sources.

However, XML data is stored in hierarchical format (as a tree using the Xquery Data Model, XDM).

1, Representing True, if the XQuery expression in a query returns a nonempty result.

We are already using XQuery to generate well-formed XML, so we could have bypassed the second transformation entirely.

And, just for fun, you'll also see how to include an XQuery with hard-coded query predicates in an application.

Be sure to consider performance concerns when you design your XQuery Web application.

eXist: Check out this open source database management system that uses XQuery.

XQuery is a friendlier, side-effect-free language tailored for transforming from one XML structure to another.

An empty script opens in the SQL and XQuery editor for the selected connection.

You can use XQuery to query XML instances stored in columns, parameters, or variables.

Additionally, the search context is not checked by using XQuery.

XQuery, in contrast, is designed to query documents and prepare reports.

Alter the generated SQL statement to include a PASSING clause in the XQuery function.

The following example explicitly converts an instance of user-defined type ComplexNumber to xml and invokes an XQuery expression over it.

XQuery and XSLT have enough developer momentum behind them that both will co-exist.

Most important, they now share a standard language, XQuery 1. 0, finally released after years of development.

Let's use a different XQuery processor to parse the content that doesn't include a built-in URL accessor method as the Qexo toolkit does.

For information about type hierarchy, see Type Casting Rules in XQuery.

The query uses XML Construction (XQuery) to construct the required XML.

You may find it easier to write such a join in plain XQuery (Query 14).

This article demonstrates the use of XQuery outside database environments using Saxon.

This kind of changing landscape is what XQuery was created to address.

Because XQuery is case-sensitive, lowercase table and column names would fail to match upper-case names in the DB2 catalog.

Once again we have used the XQuery to embed both output layout and business logic in one query.

Use of XQuery does not preclude the developer from using XSLT for transformation.

Also, a variety of mature XQuery offerings already exist.

It also allows for the use of SQL with XML extensions, Xquery and Xpath to access relational and XML data.

Use Xquery over values of UDT instances after conversion to the xml data type.

Before I wrap up this section, use XQuery to filter your XML data and to return a specific element only.

Additionally, an XQuery Update expression can delete the subtree from the each PDBML document inserted into the pdbxml table.

The namespace keyword in the XQuery prolog defines a namespace prefix.

When running as a top-level language, XQuery needs to have a source of input data.