XQuery Interview Questions And Answers

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XQuery Interview Questions and Answers

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XQuery Interview Questions And Answers

Page 1

Questions 1 How you define atomic values?

Answer
 Consider the example that have written given below:
<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
<book>
  <title lang="en">Jungle Book</title>
  <author>Rudyard Kipling</author> 
  <year>1894</year>
  <price>99.89</price>
</book>
</bookstore>
 
 Atomic values are those nodes which have no children and parent.
Example:
 Atomic values from above examples are:
Rudyard Kipling
"en"

Questions 2 How you define terms in XQuery?

Answer
 Ther are seven kinds of nodes in XQuery.These are,
1.element
2.attribute
3.text
4.namespace
5.comment
6.document or root 
7.processing-instruction nodes

 Now, consider an XML example that I have given below: 
<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
<book>
  <title lang="en">Jungle Book</title>
  <author>Rudyard Kipling</author> 
  <year>1894</year>
  <price>99.89</price>
</book>
</bookstore>
 In the above example nodes are:
<bookstore>                       (document node)
<author>Rudyard Kipling</author>  (element node)
lang="en"                         (attribute node)

Questions 3 What do you mean by selecting and Filtering elements in XQuery?

Answer
 We can selecting and filtering the xml elements with FLWOR and Path expression.
I have given you a FLWOR expression:
for $a in doc("bookmart.xml")/bookstore/book
where $a/price<150
order by $a/title
return $a/title
Where,
1. for : It is an optional and use to bind a variable to each item.
for $a in (1 to 5)
return <test>{$a}</test>

Output:
<test>1</test>
<test>2</test>
<test>3</test>
<test>4</test>
<test>5</test>
 Using at keyword we can also count the iterations.
for $a at $b in doc("bookmart.xml")/bookstore/book/title
return <book>{$b}. {data($a)}</book>

Output:
<book>1. Jungle Book</book>
<book>2. The Book of the Thousand Nights and a Night</book>
<book>3. XPath and XPointer</book>
<book>4. XML Programing</book>
 We can also use more than one expressions with for and seperate expressions using comma(,).
for $a in (5,10), $b in (50,100)
return <test>a={$a} and b={$b}</test>

Output:
<test>a=5 and b=50</test>
<test>a=5 and b=100</test>
<test>a=10 and b=50</test>
<test>a=10 and b=100</test>

2. let : It is an optional.
 let $a := (1 to 6)
return <test>{$a}</test>

Output:
<test>1 2 3 4 5 6</test>

3. where : It is an optional.Which are use to define a criteria.
where $a/price>50 and $a/price<150

4. order by : It is an optional.Which is used to set our result in sort-order.
 for $a in doc("bookmart.xml")/bookstore/book
order by $a/@category, $a/title
return $a/title

Output:
<title lang="en">The Book of the Thousand Nights and a Night</title>
<title lang="en">Jungle Book</title>
<title lang="en">XPath and XPointer</title>
<title lang="en">XML Programing</title>

5. return : It is use to define whats the result or return the result.
for $a in doc("bookmart.xml")/bookstore/book
return $a/title

Output:
<title lang="en">Jungle Book</title>
<title lang="en">The Book of the Thousand Nights and a Night</title>
<title lang="en">XPath and XPointer</title>
<title lang="en">XML Programing</title>

Questions 4 How to define functions in XQuery?

Answer
 XML has many build-in functions. XQuery functions generally made perform with string values, numeric values, date and time comparisons, boolean values etc.
 XQuery has also give us facility to made our own functions.
 Now, I told you how to call XQuery functions.
Ex 1: When you use function in an element.
<name>{uppercase($booktitle)}</name>

Ex 2: When you use function in the predicate of a path expression.
doc("bookmart.xml")/bookstore/book[substring(title,1,5)='Jungle']

Ex 3: When you use function in a let clause
let $name := (substring($booktitle,1,4))

 Now, I told you how to made functions with XQuery.
Write some points in mind when you created any functions:
Point1 : Starting with declare function keyword.
Point2 : We should prefix the function name.
Point3 : Data type of parameter should be same as data type that you defined in XML data.
Point4 : To body of the function between the curly braces.
Syntax:
declare function prefix:function_name($parameter AS datatype)
  AS returnDatatype
{
(: ...Here write function code... :)
};

Example:
declare function local:minPrice(
  $price as xs:decimal?,
  $discount as xs:decimal?)
  AS xs:decimal?
{
let $disc := ($price * $discount) div 100
return ($price - $disc)
};
(: Now, below I told you how you call the above functoin :)
<minPrice>{local:minPrice($book/price, $book/discount)}</minPrice>

Questions 5 How to add elements and attributes with XQuery in XML data?

Answer
 Consider the example "bookmart.xml".I write an expression to return litle and lang elements both.
for $a in doc("bookmart.xml")/bookstore/book/title
order by $a
return $a

Output:
<title lang="en">Jungle Book</title>
<title lang="en">The Book of the Thousand Nights and a Night</title>
<title lang="en">XPath and XPointer</title>
<title lang="en">XML Programing</title>
 
 Now, I will told you how  to add elements and attributes in XML document by using XQuery.

To add elements using XQuery : I have given you example to add some HTML elements.Like:
<html>
<body>
<h1>Bookstore</h1>
<ul>
{
for $a in doc("bookmart.xml")/bookstore/book
order by $a/title
return <li>{data($a/title)}. Category: {data($a/@category)}</li>
}
</ul>
</body>
</html>

Now, the output generated through this XQuery will be:
<html>
<body>
<h1>Bookstore</h1>
<ul>
<li>Jungle Book. Category: CHILDREN</li>
<li>The Book of the Thousand Nights and a Night. Category: ADVENTURE</li>
<li>XPath and XPointer. Category: WEB PROGRAMING</li>
<li>XML Programing. Category: WEB PROGRAMING</li>
</ul>
</body>
</html>

To add attributes using XQuery : I explain you with an example.In this example we add attributes into an HTML elements.
<html>
<body>
<h1>Bookstore</h1>
<ul>
{
for $a in doc("bookmart.xml")/bookstore/book
order by $a/title
return <li class="{data($a/@category)}">{data($a/title)}</li>
}
</ul>
</body>
</html>

Now, the HTML elements will looks like:
<html>
<body>
<h1>Bookstore</h1>
<ul>
<li class="CHILDREN">Jungle Book</li>
<li class="ADVENTURE">The Book of the Thousand Nights and a Night</li>
<li class="WEB PROGRAMING">XPath and XPointer</li>
<li class="WEB PROGRAMING">XML Programing</li>
</ul>
</body>
</html>