XQuery Interview Questions and Answers

This section covers frequently asked XQuery interview questions.

1. What is XQuery?

XQuery is a query language for XML data. It's similar to SQL for relational databases but is designed for working with XML's hierarchical structure.

2. Uses of XQuery.

  • Retrieving data from XML documents.
  • Generating reports from XML data.
  • Transforming XML to other formats (like HTML).
  • Working with XML-based databases.

3. XQuery's First Appearance.

XQuery 1.0 became a W3C Recommendation in January 2007.

4. XQuery Syntax Rules.

  • Case-sensitive.
  • Uses valid XML names for elements and attributes.
  • Strings enclosed in single or double quotes.
  • Variables start with a dollar sign ($).
  • Comments use `(: ... :)`.

5. XQuery vs. XPath.

Feature XQuery XPath
Type Query language Navigation language
Purpose Data extraction and manipulation Node selection

6. XQuery vs. XSLT.

Feature XQuery XSLT
Focus Data retrieval Data transformation

7. Defining Functions in XQuery.

(This section would describe how to define functions in XQuery, including parameter declarations and return types.)

8. Calling XQuery Functions.

(This section would show examples of calling XQuery functions within different contexts like path expressions, let clauses, and within elements.)

9. Comparisons in XQuery.

XQuery supports both general comparisons (=, !=, <, >, etc.) and value comparisons (eq, ne, lt, etc.).

10. Types of Queries Solved by XQuery.

(This section lists the types of queries that XQuery is commonly used to solve.)

11. FLWOR Expression.

FLWOR (FOR, LET, WHERE, ORDER BY, RETURN) is a core construct in XQuery for specifying queries, providing a structured way to express complex data retrieval and manipulation operations.

12. XQuery HTML Format.

(This section would describe how to generate HTML output using XQuery.)

13. Selecting and Filtering Elements.

XQuery uses path expressions and FLWOR expressions for selecting and filtering elements within an XML document.

14. Conditional Operations (If-Then-Else).

Example

if (condition) then {result1} else {result2}

15. XQuery Syntax.

(This section would reiterate the basic syntax rules of XQuery, such as case sensitivity and valid XML naming conventions.)

16. XQuery add.

(This section would discuss the XQuery `add` function used to add nodes to the result tree.)

17. XQuery FLWOR with HTML.

(This would show how to incorporate HTML elements within an XQuery FLWOR expression to generate formatted HTML output.)

18. Types of XQuery Functions.

(This section would list various categories of XQuery functions: Accessor, Error, Numeric, String, etc.)

19. Date and Time Functions.

  • current-date()
  • current-time()
  • current-dateTime()

20. current-date() Function.

Returns the current date.

21. current-time() Function.

Returns the current time.

22. current-dateTime() Function.

Returns the current date and time.

23. XPath vs. FLWOR Expressions.

(This section would compare the relative strengths of XPath expressions, which are focused on locating specific nodes within an XML document, and FLWOR expressions, which provide a more structured approach to selecting, filtering, sorting, and manipulating XML data.)

24. Nodes in XQuery.

Elements, attributes, text, namespaces, processing instructions, comments, and the document node are all considered nodes in an XML document.

25. Types of Nodes.

(This section would list the different node types: element, attribute, text, namespace, processing-instruction, comment, and document.)

26. Atomic Values.

Atomic values are simple values (like strings or numbers) in XQuery, distinct from nodes.

27. Node Relationships.

(This section would describe various node relationships, including parent, child, sibling, ancestor, and descendant.)

28. Selecting Books with Price Under $30.

XQuery

doc("books.xml")/bookstore/book[price < 30]

29. Example FLWOR Expression.

XQuery

for $book in doc("books.xml")/bookstore/book
where $book/price > 60
order by $book/category
return $book/category

30. for Clause.

The `for` clause iterates over a sequence of nodes.

31. order by Clause.

The `order by` clause sorts the results of a query.

32. Mandatory Clause in FLWOR.

The `return` clause is mandatory because it specifies what data the query should return.