select distinct in XQuery?

, ,
1

Hi,
I have a problem.
I need to eliminate double node-sets in my XQuery Result but the dinstinct-values() function only works with atomic-values!
Is there a simple option like the select distinct in SQL?

Thanks
tovo

2

Hi,

You can eliminate duplicate nodes by applying a path expression. An according query may look like this:

(for $a in input()/bib/book return $a, for $a in input()/bib/book return $a)/.

The path expression applied on the flwr expression removes all duplicate “book” elements and sorts the resulting node sequence in document order.

Best regards,

Thorsten Fiebig

3

Thanks for the answer but it does’t work.
I have a document like

Databases 10
4

Hi,

To perform a value-based duplicate elimination you have to apply the distinct-values() function. For your example I would suggest the following query:

for $dt in input()/book/title
for $dp in input()/book/price
let $g := input()/book[title =$dt and price = $dp]
where $g
return
{$dt, $dp}

The two “for” clauses retrieve all distinct book titles and prices. The result is a cross-product over the two distinct value sets. The “let” clause retrieves for each combination of “title” and “price” the according “book” elements. By referencing the variable $g in the “where” clause you perform a none-empty check on the node set determined by the “let” clause. Hence, you create a “BookInformation” element just for the existing combinations of “title” and “price”.

Best regards,

Thorsten Fiebig