XQuery Functions: A Comprehensive Guide 🎯

Welcome to the XQuery Functions tutorial! In this lesson, we'll delve into the world of XQuery functions, understanding their importance, and learning how to use them effectively. Let's get started! 📝

What are XQuery Functions? 💡

XQuery functions are reusable pieces of code that perform specific tasks on XML documents. They can be defined locally within a query or globally in a module. XQuery functions are essential for handling complex XML data efficiently and effectively.

Basic Function Syntax 💡

A basic function declaration looks like this:

xquery

declare function local:functionName(parameters) {
    // Function body
}

Let's create a simple function that calculates the sum of two numbers:

xquery

declare function local:add($num1 as xs:integer, $num2 as xs:integer) {
    $num1 + $num2
}

XQuery Built-in Functions 💡

XQuery comes with a rich library of built-in functions that can help you perform various operations on XML data. Let's explore some of them:

1. `doc()` function 💡

The doc() function is used to load an XML document.

Example:

xquery

let $doc = doc("<root><element>Hello</element></root>")
return $doc/element

2. `fn:count()` function 💡

The count() function returns the number of elements in a sequence.

Example:

xquery

let $doc = doc("<root><element1>A</element1><element2>B</element2><element3>C</element3></root>")
return count($doc/element*)

Practical Use Cases 💡

Now that we've covered the basics, let's dive into some practical use cases.

Example 1: Filtering XML Data 💡

Suppose we have an XML document containing employee data:

xml

<employees>
    <employee id="1">
        <name>John</name>
        <position>Manager</position>
        <salary>50000</salary>
    </employee>
    <employee id="2">
        <name>Mike</name>
        <position>Developer</position>
        <salary>40000</salary>
    </employee>
    <employee id="3">
        <name>Lisa</name>
        <position>Designer</position>
        <salary>35000</salary>
    </employee>
</employees>

We can create a function to find the employee with the highest salary:

xquery

declare function local:highestSalaryEmployee($employees as element()) {
    $maxSalary := 0
    $maxSalaryEmployee := ()
    for $employee in $employees/employee
    let $salary := $employee/salary
    if ($salary > $maxSalary) then
        return $employee
    return $maxSalaryEmployee
}

Example 2: Transforming XML Data 💡

Suppose we have an XML document with a list of products:

xml

<products>
    <product id="1">
        <name>Product A</name>
        <price>100</price>
    </product>
    <product id="2">
        <name>Product B</name>
        <price>200</price>
    </product>
    <product id="3">
        <name>Product C</name>
        <price>300</price>
    </product>
</products>

We can create a function to convert the product list into a comma-separated list of product names and prices:

xquery

declare function local:productListToCSV($products as element()) {
    $csv := ""
    for $product in $products/product
    let $name := $product/name
    let $price := $product/price
    let $formattedPrice := concat($price, ",\"", $name, "\"")
    if (not($csv =="")) then
        let $formattedCSV := concat($csv, ",", $formattedPrice)
        return $formattedCSV
    return $formattedPrice
}

Quiz Time 💡

Happy learning! ✅

XQuery Functions: A Comprehensive Guide 🎯

XQuery Functions: A Comprehensive Guide 🎯

What are XQuery Functions? 💡

Basic Function Syntax 💡

XQuery Built-in Functions 💡

1. doc() function 💡

2. fn:count() function 💡

Practical Use Cases 💡

Example 1: Filtering XML Data 💡

Example 2: Transforming XML Data 💡

Quiz Time 💡

1. `doc()` function 💡

2. `fn:count()` function 💡