[xquery-talk] Function and Query Evaluation with No XML Tags Error

Fri Feb 29 10:03:14 PST 2008

________________________________________
From: Michael Kay [mike at saxonica.com]
Sent: Friday, February 29, 2008 8:57 AM
To: Wei, Alice J.; 'Kevin Grover'
Cc: talk at x-query.com
Subject: RE: [xquery-talk] Function and Query Evaluation with No XML Tags Error

I've rather lost track of the requirement. I think you can do

declare function local:unique-nodes-by-value($seq as element()*) as
element()* {
  for $d in distinct-values($seq)
  return $seq[. = $d][1]
};

   Are you suggesting me to forget about "order by"?

That is, for each distinct value return the first element having that value.

    I think one of the issues with the data is that some have attributes of @type that says main and some say sub while others may have neither while it is ranking. The code I tried above is still parsing elements in the order they appear and not their actual "order."

  It may not be the problem, but to illustrate this issue, I have a short XML clip below:

XML:

<ad>
<head type ="main"> A Free Ticket to your Favorite Pro Sports Game in Every Sugar Daddy Pop! </head>
<head type ="sub">Basketball! Hockey! Lacrosse! Soccer! Pro track and more! </head>

</ad>

XQuery:

declare variable $data := doc("1.xml")//ad;

declare variable $s := $data/child::head[contains(upper-case(.), 'BASKET')];

declare function local:unique-nodes-by-value($seq as element()*) as element()*
{
for $d in distinct-values($seq)
 return <ad>{$seq[. = $d][1]}</ad>
};

local:unique-nodes-by-value($s)

Current Output:

<ad>
      <head type="sub">Basketball! Hockey! Lacrosse! Soccer! Pro track and more! </head>
   </ad>

Intended Output:

<ad>
<head type ="main"> A Free Ticket to your Favorite Pro Sports Game in Every Sugar Daddy Pop! </head>
<head type ="sub">Basketball! Hockey! Lacrosse! Soccer! Pro track and more! </head>
</ad>

Thanks again.

Michael Kay
http://www.saxonica.com/

> -----Original Message-----
> From: Wei, Alice J. [mailto:ajwei at indiana.edu]
> Sent: 29 February 2008 13:47
> To: Michael Kay; 'Kevin Grover'
> Cc: talk at x-query.com
> Subject: RE: [xquery-talk] Function and Query Evaluation with
> No XML Tags Error
>
> Hi, Michael:
>
>   I found the method Kevin provided even in the output his
> extracted still not even ranked, so I guess maybe going back
> to distinct-values() may be the way to go.
>
>   Is this inside the function itself?
>
> Here is the XQuery:
>
> declare variable $data := doc("1.xml")//ad;
>
> declare variable $s := $data//head[contains(upper-case(.), 'BOOK')];
>
> declare function local:unique-nodes-by-value($seq as
> element()*) as element()* {
> $seq[not(string(.)=preceding-sibling::*/string(.))]
> };
>
> local:unique-nodes-by-value($s)
>
> Output:
>
> <?xml version="1.0" encoding="UTF-8"?>
>    <head type="sub">Comic Book Back issues</head>
>    <head type="sub">We Buy and Sell Comic Books</head>
>    <head type="sub">FREE BOOK</head>
>    <head type="sub"> GIANT NEW COMIC BOOK CATALOG #6</head>
>    <head type="main"> Selling - COMIC BOOKS -Buying <lb/>
> $100,000 Inventory<lb/>
>                         Marvel, D.C., Golden Age </head>
>    <head type="main">COMIC Books</head>
>    <head>COMIC BOOKS Wanted</head>
>    <head type="main">OLD Comic Books!</head>
>    <head>Old Comic Books</head>
>
> ======================================================
> Alice Wei
> MIS 2008
> School of Library and Information Science Indiana University
> Bloomington ajwei at indiana.edu ________________________________________
> From: Michael Kay [mike at saxonica.com]
> Sent: Friday, February 29, 2008 4:30 AM
> To: 'Michael Kay'; 'Kevin Grover'; Wei, Alice J.
> Cc: talk at x-query.com
> Subject: RE: [xquery-talk] Function and Query Evaluation with
> No XML Tags Error
>
> > Assuming that the typed value is the same as the string
> value, you can
> > write
> >
> > $seq[not(. = preceding-sibling::*)]
> >
> > If you really need the string value, it's
> >
> > $seq[not(./string() = preceding-sibling::*/string())]
> >
> > But using distinct-values() is likely to be a lot more efficient.
> >
>
> Actually, I failed to spot another error here. The author of
> the function has no way of knowing that the nodes in $seq
> will be siblings of each other.
> Therefore, using preceding-sibling to eliminate duplicates is
> not just inefficient, it is plain wrong.
>
> Michael Kay
> http://www.saxonica.com/
>