XQuery Language Reference.pdf

XQuery Language Reference

SQL Server 2012 Books Online

Summary : XQuery is a language that can query structured or semi-structured XML data.

With the xml data type support provided in the Database Engine, documents can be

stored in a database and then queried by using XQuery. XQuery is based on the existing

XPath query language, with support added for better iteration, better sorting results,

and the ability to construct the necessary XML.

Category: Reference

Applies to : SQL Server 2012

Source : SQL Server Books Online ( link to source content )

E-book publication date : June 2012

without the written permission of the publisher.

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Contents

XQuery Language Reference (SQL Server) ............................................................................................................6

XQuery Basics ...................................................................................................................................................................8

Sequence and QNames ............................................................................................................................................9

Expression Context and Query Evaluation...................................................................................................... 12

Atomization ................................................................................................................................................................ 16

Effective Boolean Value ......................................................................................................................................... 18

Type System ............................................................................................................................................................... 19

Sequence Type Matching.................................................................................................................................. 23

Error Handling ........................................................................................................................................................... 32

Comments in XQuery.............................................................................................................................................. 34

XQuery and Static Typing ..................................................................................................................................... 35

XQuery Expressions ..................................................................................................................................................... 38

Primary Expressions................................................................................................................................................. 39

Path Expressions ....................................................................................................................................................... 43

Specifying Axis in a Path Expression Step................................................................................................... 45

Specifying Node Test in a Path Expression Step ...................................................................................... 50

Specifying Predicates in a Path Expression Step ...................................................................................... 59

Using Abbreviated Syntax in a Path Expression ....................................................................................... 64

Sequence Expressions ............................................................................................................................................ 66

Arithmetic Expressions ........................................................................................................................................... 71

Comparison Expressions........................................................................................................................................ 72

Logical Expressions.................................................................................................................................................. 78

XML Construction..................................................................................................................................................... 79

FLWOR Statement and Iteration......................................................................................................................... 94

Ordered and Unordered Expressions .............................................................................................................107

Conditional Expressions.......................................................................................................................................107

Quantified Expressions.........................................................................................................................................111

SequenceType Expressions.................................................................................................................................113

Validate Expressions..............................................................................................................................................123

Modules and Prologs................................................................................................................................................123

XQuery Prolog .........................................................................................................................................................124

Type Casting Rules in XQuery ...............................................................................................................................126

XQuery Functions against the xml Data Type .................................................................................................131

Functions on Numeric Values............................................................................................................................133

ceiling Function...................................................................................................................................................133

floor Function.......................................................................................................................................................135

round Function....................................................................................................................................................136

XQuery Functions on String Values.................................................................................................................137

concat Function...................................................................................................................................................137

contains Function ...............................................................................................................................................140

substring Function .............................................................................................................................................142

string-length Function......................................................................................................................................144

lower-case Function .........................................................................................................................................148

upper-case Function ........................................................................................................................................150

Functions on Boolean Values.............................................................................................................................152

not Function .........................................................................................................................................................152

Functions on Nodes ..............................................................................................................................................154

number Function ................................................................................................................................................155

local-name Function..........................................................................................................................................157

namespace-uri Function ..................................................................................................................................158

Context Functions ..................................................................................................................................................160

last Function .........................................................................................................................................................161

position Function................................................................................................................................................162

Functions on Sequences......................................................................................................................................164

empty Function ...................................................................................................................................................164

distinct-values Function...................................................................................................................................167

id Function ............................................................................................................................................................168

Aggregate Functions.............................................................................................................................................173

count Function ....................................................................................................................................................173

min Function ........................................................................................................................................................176

max Function........................................................................................................................................................177

avg Function.........................................................................................................................................................178

sum Function........................................................................................................................................................179

Data Accessor Functions......................................................................................................................................182

string Function.....................................................................................................................................................182

data Function .......................................................................................................................................................185

Constructor Functions ..........................................................................................................................................188

Boolean Constructor Functions.........................................................................................................................192

true Function........................................................................................................................................................192

false Function.......................................................................................................................................................194

expanded-QName .............................................................................................................................................195

local-name-from-QName ...............................................................................................................................199

namespace-uri-from-QName........................................................................................................................201

SQL Server XQuery Extension Functions .......................................................................................................201

sql:column() Function .......................................................................................................................................202

sql:variable() Function.......................................................................................................................................205

XQuery Operators Against the xml Data Type................................................................................................207

Additional Sample XQueries Against the xml Data Type............................................................................209

General XQuery Use Cases .................................................................................................................................209

XQueries Involving Hierarchy ............................................................................................................................219

XQueries Involving Order....................................................................................................................................221

XQueries Handling Relational Data.................................................................................................................228

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