XQuery statement that groups results - group-by

Question

I have an XML structure that I need to query using XQuery.
As far as I have been able to find, this may not even be possible, but since I am so new to XQuery I thought I may ask.
I need to query the XML below and return something that looks like:
<product>
<title>Acer Liquid</title>
<image>ACER-LIQUID.jpg</image>
<networks>
<network>O2O</network>
<network>VOD</network>
</networks>
<colours>
<colour>Blue</colour>
<colour>Black</colour>
</colours>
</product>
So my query is essentially something like:
Get all product details where there is a salespackage that belongs to "Pay Monthly" that points to it (via main_product), and attach the network property from each sales package that points to it. But group the results by the product.product_model field.
Source XML:
<root>
<package>
<title>package1</title>
<categories><category group="Other" name="Pay Monthly"/></categories>
<properties>
<value key="main_product">PRODUCT#14649766#PART#ACERLIQUIDBLACK</value>
<value key="network_code">O2O</value>
</properties>
</package>
<package>
<title>package2</title>
<categories><category group="Other" name="Pay Monthly"/></categories>
<properties>
<value key="main_product">PRODUCT#14649700#PART#ACERLIQUIDBLUE</value>
<value key="network_code">VOD</value>
</properties>
</package>
<product>
<title>Acer Liquid</title>
<properties>
<value key="product_code">PRODUCT#14649700#PART#ACERLIQUIDBLUE</value>
<value key="product_model">Acer Liquid|ACER_LIQUID</value>
<value key="product_image_url">ACER-LIQUID.jpg</value>
<value key="colour">Blue</value>
</properties>
</product>
<product>
<title>Acer Liquid</title>
<properties>
<value key="product_code">PRODUCT#14649766#PART#ACERLIQUIDBLACK</value>
<value key="product_model">Acer Liquid|ACER_LIQUID</value>
<value key="product_image_url">ACER-LIQUID.jpg</value>
<value key="colour">Black</value>
</properties>
</product>
</root>

Answer 1

Quite complex query for XQuery 1.0:
declare ordering unordered;
declare function local:values($items as node()*,
$property as xs:string) as xs:string* {
distinct-values($items/properties/value[#key eq $property])
};
declare function local:filter($items as node()*,
$property as xs:string,
$values as xs:string*) as node()* {
$items[properties/value[#key eq $property] = $values]
};
let $packages := doc('source')/root/package[categories/category[#name eq 'Pay Monthly']]
let $products := local:filter(doc('source')/root/product,
'product_code',
local:values($packages, 'main_product'))
for $model in local:values($products, 'product_model')
let $model_products := local:filter($products, 'product_model', $model)
let $model_packages := local:filter($packages,
'main_product',
local:values($model_products, 'product_code'))
return
<product>
{$model_products[1]/title}
<image>{local:values($model_products[1], 'product_image_url')}</image>
<networks>{
for $net in local:values($model_packages, 'network_code')
return <network>{$net}</network>
}</networks>
<colours>{
for $cl in local:values($model_products, 'colour')
return <colour>{$cl}</colour>
}</colours>
</product>

Answer 2

This XQuery:
for $title in (/root/product/title)[index-of(/root/product/title,.)[1]]
let $ProductsProp := /root/product[title=$title]/properties/value
return
<product>
{$title}
<image>{string(($ProductsProp[#key='product_image_url'])[1])}</image>
<networks>{
for $network in /root/package/properties
[value[#key='main_product']
= $ProductsProp[#key='product_code']]
/value[#key='network_code']/string()
return
<network>{$network}</network>
}</networks>
<colours>{
for $colour in $ProductsProp[#key='colour']/string()
return
<colour>{$colour}</colour>
}</colours>
</product>
Output:
<product>
<title>Acer Liquid</title>
<image>ACER-LIQUID.jpg</image>
<networks>
<network>O2O</network>
<network>VOD</network>
</networks>
<colours>
<colour>Blue</colour>
<colour>Black</colour>
</colours>
</product>
Note: XPath 2.0 grouping expression $vSeq[index-of($vSeq,.)[1]]