1. Dirt, Spit, and Happy FLWOR
Hands on with XQuery
Dirt, Spit, and Happy FLWOR

2. Presentation Rating:
ADVANCED
INTERMEDIATE
BEGINNER

3. Presentation Rating:

4. Purpose Introduce the basic syntax of FLWOR, the XQuery language.
Interfaces with T-SQL
Basic functions
We won’t be covering conversion of SQL to XML (FOR XML…)
No tricks or tips

5. Why Me?
Data Architect working in the field of financial information security
Prior experience as DBA and a reporting/database developer
AtlantaMDF Chapter Leader
Tutor, not a teacher

6. Assumptions About You
Database professional (DBA, database developer, BI specialist)
Some experience with XML

7. Let’s Review
“Gentlemen, this is a football.” – Vince Lombardi

8. Basic XML Structure
<root> <tag>This is an element</tag> <tag att=“attribute”> Another element</tag> </root> Elements and Attributes are both nodes.

9. Basic XML Structure XML can be Typed or Untyped
Untyped = xml fragments; WYSIWYG
Typed = validation of datatypes, relationships
Typed XML requires a Schema
SQL Server supports Schema
SQL Server supports inline DTD
Namespaces
Used for providing uniquely named elements and attributes in an XML document

10. XML in SQL Server 2000+ Generation: Translation: FOR XML OPENXML
RAW, AUTO, EXPLICIT
Translation:
OPENXML
sp_xml_preparedocument
sp_xml_removedocument

11. XML in SQL Server 2005+ Generation: Translation: FOR XML xml datatype
PATH
TYPE
Translation:
xml datatype
XQuery

12. XML Translation xml datatype Well-formed fragments (no root required)
2 GB maximum
Cannot be compared or sorted
Supports conversion to (n)varchar(max)
Required for XQuery

13. XML Translation XQuery Complete query language outside of SQL Server
SQL Server implements limited subset
xml methods
exist()
value()
query()
nodes()
modify() (beyond scope of presentation)

14. XML Translation
SQL engine interfaces with XML engine

15. XML Translation
XML method
Syntax
Returns
.exist()
.exist(XQuery)
bit: 1 if True, 0 if False, NULL if xml is NULL
.value()
.value(XQuery, SQLtype)
SQL data type: specified as a parameter in method
.query()
.query(XQuery)
XML: 1 fragment per row
.nodes()
.nodes(XQuery) as Table(column)
XML: each node becomes a new row
Primary purpose of XQuery in SQL Server is to convert XML data to a tuple in a dataset.
For robust handling of XML, use another tool.

16. FLWOR
“Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler

17. FLWOR For Let Where Order By Return Context switches ({})
Primary Language
Other Components
For
Let
Where
Order By
Return
Context switches ({})
Functions (data(), position())
Positional References ([ ])
SQL Server’s implementation of XQuery is a limited subset; it improved between
2005 and 2008, but several functions are still not available.

18. Positional References []
XML = '<Families> <Family name="Ainsworth"> <Parent name="Stuart"> <Child name="Isabel"/> <Child name="Grace"/> </Parent> </Family> <Family name="Smith"> <Parent name="Aaron"> <Child name="John"/> </Families>' SELECT 'varchar(100)'), 'varchar(100)')

19. Context switches {}
XML = '<Families> <Family name="Ainsworth"> <Parent name="Stuart"> <Child name="Isabel"/> <Child name="Grace"/> </Parent> </Family> <Family name="Smith"> <Parent name="Aaron"> <Child name="John"/> </Families>'

20. Context switches {}
<New> <Family name="Ainsworth"> <Parent name="Stuart"> <Child name="Isabel" /> <Child name="Grace" /> </Parent> </Family> </New>

21. (for)(let)… return
FLWOR requires either for or let and a return statement
return returns the actual dataset
{for $f in /Families
return "Hello World!"}
</root> ')
<root>Hello World!</root>

22. for for is an iterative operator
Used to assign elements into a variable
Step through that variable
{for $f in /Family
return "Hello World!"}
</root> ')
<root>Hello World! Hello World!</root>

23. let let assigns a value to a variable
Introduced in SQL 2008
$f in //Family
let
return $n}
</root> ')
<root>Ainsworth Smith</root>

24. Pop Quiz!
<Families> <Family name="Ainsworth"> <Parent name="Stuart" /> </Family> <Family name="Smith"> <Parent name="Aaron" /> </Families> $f in //Family let for $p in $f/Parent return " ", $n)}</Person>} </root>')

25. Pop Quiz!
<root> <Person>Stuart Ainsworth</Person> <Person>Aaron Smith</Person> </root>

26. where Similar to WHERE clause in SQL
XML = '<Families>
<Family name="Ainsworth">
<Parent name="Stuart">
<Child name="Isabel"/>
<Child name="Grace"/>
</Parent>
</Family>
<Family name="Smith">
<Parent name="Aaron">
<Child name="John"/>
</Families>'

27. where <root> <Person>Isabel Ainsworth</Person>
$f in //Family
let
for $c in $f/Parent/Child where $n="Ainsworth" return " ", $n)}</Person>}
</root>')
<root>
<Person>Isabel Ainsworth</Person>
<Person>Grace Ainsworth</Person>
</root>

28. order by SELECT @x.query('<root>{for $f in //Family
let
for $c in $f/Parent/Child where $n="Ainsworth“
order by
return " ", $n)}</Person>}
</root>')
<root>
<Person>Grace Ainsworth</Person>
<Person>Isabel Ainsworth</Person>
</root>

29. More stuff to learn
“A child of five would understand this. Send someone to fetch a child of five.”
- Groucho Marx

30. Functions ceiling, floor, round concat, contains, substring
lower-case Function (XQuery)
string-length
upper-case Function (XQuery)
not
number
local-name Function (XQuery)
namespace-uri Function (XQuery)
last
position
empty
distinct-values
id Function (XQuery)
count
avg, min, max, sum
string, data
true Function (XQuery)
false Function (XQuery)
expanded-QName (XQuery)
local-name-from-QName (XQuery)
namespace-uri-from-QName (XQuery)
sql:column() function (XQuery)
sql:variable() function (XQuery)

31. sql:variable()
XML = '<Loc id="1">Atlanta</Loc> <Loc INTEGER = 1 $l in /Loc where return data($l)}</root>') $l in /Loc where
<root>Washington</root>
<root>Atlanta</root>

32. sql:column()
XML = '<Loc id="1">Atlanta</Loc> <Loc id="2">Washington</Loc>' TABLE (ID INTEGER) INSERT (ID) VALUES(1), (2) $l in /Loc where return data($l)}</root>') T _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ <root>Atlanta</root> <root>Washington</root>

33. Pop Quiz! DECLARE @x XML = '<row>A</row>
<row>B</row>
<row>C</row>
<row>D</row>
<row>E</row> '
TABLE (ID INT)
INSERT (ID)
SELECT ROW_NUMBER() OVER (ORDER BY c.column_id )
FROM sys.columns c
[position()=sql:column("T.ID")]') t
WHERE t.ID {count(/row)} </r>').value('.', 'int')

34. Pop Quiz! <row>A</row> <row>B</row>
<row>C</row>
<row>D</row>
<row>E</row>

35. Questions?
“It’s a miracle that curiosity survives formal education.” – Albert Einstein

36. Contact Information
Stuart R Ainsworth