eXist Xquery Examples

以下 ex:> 代表输入表达式 re:> 表示输出结果

_ -- _ _ 插入 [ _ _ 使用 exist _ _ 的 xquery _ _ 数据库检索工具 ] _ _ 说明 -- _

[ 基础操作 ]

** 1 ** ** 条件表达式 **

ex:>if (3 < 4) then "yes!" else "no!"

re:>yes!

ex:>

for $x in (-1.5, 0.4, 1.7)

return

 1<amount>
 2
 3{ 
 4
 5if ($x &lt; 0) 
 6
 7then concat("(", -$x, ")") 
 8
 9else $x 
10
11} </amount>

re:>

1<amount>(1.5)</amount>

1<amount>0.4</amount>

1<amount>1.7</amount>

说明：注意第一行的输出和其它两行有所不同

-$x 对 $x 取反

** 2 ** ** 定义本地变量 **

ex:>let $x := 5 let $y := 6 return 10*$x+$y

re:>56

** 3 ** ** 使用 "," ** ** ，其功能相当于数组 **

ex:>3,4,5

re:>3

扩展加入其它语句

ex:>3,4,5,let $t:=56 return $t

re:>3

** 4 ** ** 在 return ** ** 中使用 {} {expression} ** ** 执行出来表达式的结果 **

ex:>

let $i := 2 return

let $r :=

1<em>Value </em>

return

1<p>{$r} of 10*{$i} is {10*$i}.</p>

re:>

1<p><em>Value </em> of 10*2 is 20.</p>

** 5 ** ** 简单循环语句 **

ex:>for $x in (1 to 3) return ($x,10+$x)

re:>1

ex:>for $speech in document("/db/tonybooks/Catalog.xml")//categoryName

return {$speech}

re:> 略

ex:>

1<html>{ 
2
3let $book := document("mybook.xml")/book 
4
5for $ch in $book/chapter 
6
7return <h2>{$ch/title)</h2>
8
9}</html>

re:> 略

** 6 ** ** 使用 text(), ** ** 返回内容 **

ex:>let $book:=document("examples.xml")/example-queries/query

return $book/code/text()

ex:>let $doc := document("examples.xml")//query/code/text()

return $doc

[ 函数的定义与调用 ]

ex:>

declare namespace jnb = "http://ociweb.com/jnb";

declare variable $jnb:pi as xs:decimal { 3.1416 };

declare function jnb:fib($i as xs:integer) as xs:integer {

if ($i = 0 or $i = 1)

then 1

else jnb:fib($i - 1) + jnb:fib($i - 2)

};

jnb:fib(3), jnb:fib(4), jnb:fib(5), $jnb:pi

re:>

3.1416

[ 节点和节点类型 ]

一下两个作用相同

ex:>

1<greeting from="weiqi">Hello, World!</greeting>

re:>

1<greeting from="weiqi">Hello, World!</greeting>

ex:> document {

element { "greeting" } {

attribute { "from " } { "weiqi" },

"Hello, World!"

}

re:>

1<greeting from="weiqi">Hello, World!</greeting>

[flwor 表达式 / 数据库检索命令 ]

标准类型 for, let, where, order by, return

** 1 for ** ** 语句 **

ex:>

for $x in (1, 2, 3)

return

1<number>{ $x }</number>

re:>

1<number>1</number>

1<number>2</number>

1<number>3</number>

** 2 let ** ** 语句 **

ex:>

let $a := (1, 2, 3)

return

1<numbers>{ $a }</numbers>

re:>

1<numbers>1 2 3</numbers>

** 3 where ** ** 语句 **

ex:>

for $x in (1, 2, 3)

where $x >= 2

return

1<number>{ $x }</number>

re:>

1<number>2</number>

1<number>3</number>

** 4 order by ** ** 语句 **

ex:>

for $x in (

1<greeting></greeting>

1<greeting from="weiqi"></greeting>

1<greeting from="brian"></greeting>

)

order by $x/@from ascending empty least

return $x

re:>

1<greeting></greeting>

1<greeting from="brian"></greeting>

1<greeting from="weiqi"></greeting>

说明 order by 有以下几个属性：

descending ， ascending ， empty greatest ， empty least

分别测试一下

[ 数量操作 ] 该操作非常有用该操作非常有用

** 1 some ** ** 和 every ** ** 例子 **

ex:>some $x in (1, 2, 3) satisfies $x >= 2

re:>true

ex:>every $x in (1, 2, 3) satisfies $x >= 2

re:>false

ex:>some $x in (1, 2, 3), $y in (3, 4, 5) satisfies $x = $y

re:>true

ex:>every $x in (1, 2, 3), $y in (3, 4, 5) satisfies $x = $y

re:>false

** 2 count($a) **

ex:>let $a:=collection("tonybooks")//category

return count($a)

re:> 返回 40 个 1

ex:>for $a in collection("tonybooks")//category

return count($a)

re:> 返回 40

区别以上例子

** 3 ** ** 多重循环语句 **

ex:>

for $c in customers

for $o in orders

where $c.cust_id=$o.cust_id and $o.part_id="xx"

return $c.name

以上语句等价于 sql 语句

select customers.name from customers, orders

where customers.cust_id=orders.cust_id and orders.part_id="xx"

ex:>

for $book in bib.xml//book

let $title := $book/title

where $book/publisher = 'Addison-Wesley'

return

1<bookinfo>{ $title }</bookinfo>

[xpath 例子 ]

greetings.xml:

1<greetings>
2<greeting from="weiqi">Nihao!</greeting>
3<greeting from="brian">Hi!</greeting>
4<greeting from="luc">Bonjour!</greeting>
5</greetings>

ex:>doc("greetings.xml")/greetings

re:>

1<greetings>
2<greeting from="weiqi">Nihao!</greeting>
3<greeting from="brian">Hi!</greeting>
4<greeting from="luc">Bonjour!</greeting>
5</greetings>

ex:>doc("greetings.xml")//greeting

re:>

1<greeting from="weiqi">Nihao!</greeting>

1<greeting from="brian">Hi!</greeting>

1<greeting from="luc">Bonjour!</greeting>

说明：注意以上两个例子的区别 /greetings 和 //greetings ，

前者表示从根节点开始逐级遍历，后者表示任何级的节点都遍历

ex:>doc("greetings.xml")//greeting[@from="weiqi"]

re:>

1<greeting from="weiqi">Nihao!</greeting>

说明： @from 用来引用节点中的属性名称

引用节点名直接输入例如： greeting 或者 greetings 就可以

ex:>doc("greetings.xml")//greeting/@from

re:>from="weiqi" from="brian" from="luc"

ex:>doc("greetings.xml")//greeting[1]

re:>

  1<greeting "[n]="" $a="" $a)="" $b="" $c="" $d="" (2,="" (3,4,3,4).="" (count($a),="" 0)="" 1,="" 4,="" :="()" \--="" as="" because="" children(<p="" count($b),="" count($c),="" count($d))="" evaluates="" from="weiqi&gt;Nihao!&lt;/greeting&gt;
  2
  3说明：使用  " is="" let="" return="" same="" the="" to="" 待查：="" 节点名="" 表示输出第几个节点内容="" 错误="">This is <em>very</em> cool.) 
  4
  5returns this sequence of 3 values: 
  6
  7"This is ", <em>very</em>, " cool." 
  8
  9================  以下为未整理部分  ============= 
 10
 11[Modules] 
 12
 13You can put functions and variables declarations into library modules. A library module is a file that starts with a module namespace declaration and contains declarations of functions, variables, etc., but does not contain an expression at the end. A main module contains an expression at the end. Both library modules and main modules can import other library modules to access variables and functions declared in the imported module. 
 14
 15(: libfib.xq :) 
 16
 17module namespace jnb = "http://ociweb.com/jnb"; 
 18
 19declare function jnb:fib($i as xs:integer) as xs:integer { 
 20
 21if ($i &lt;= 1) 
 22
 23then 1 
 24
 25else jnb:fib($i - 1) + jnb:fib($i - 2) 
 26
 27}; 
 28
 29(: mainfib.xq: ) 
 30
 31import module namespace jnb = "http://ociweb.com/jnb" at "libfib.xq"; 
 32
 33jnb:fib(6) 
 34
 35[weiqi@gao] $ xquery mainfib.xq  # Saxon 
 36
 3713 
 38
 39Qexo supports compiled modules. A library module is compiled to a Java class whose name is derived from the module namespace URI. A main module is compiled to a Java class whose name is derived from the module file name. 
 40
 41[weiqi@gao] $ qexo -C libfib.xq  # Compile to Java class com.ociweb.jnb 
 42
 43(compiling libfib.xq) 
 44
 45[weiqi@gao] $ qexo --main -C mainfib.xq  # Compile to Java class mainfib 
 46
 47(compiling mainfib.xq) 
 48
 49[weiqi@gao] $ java mainfib 
 50
 5113 
 52
 53\------------------------------------------------------------------------- 
 54
 55Type Specification 
 56
 57XQuery is a strongly typed programming language. Like Java and C#, for example, it's a mix of static typing (type consistency checked at compile-time) and dynamic typing (run-time type tests). However, the types in XQuery are different from the classes familiar from object-oriented programming. Instead, it has types to match XQuery's data model, and it allows you to import types form XML Schema. 
 58
 59if ($child instance of element section) 
 60
 61then process-section($child) 
 62
 63else ( ) {--nothing--} 
 64
 65This invokes the process-section function if the value of $child is an element whose tag name is section. XQuery has a convenient typeswitch shorthand for matching a value against a number of types. The following converts a set of tag names to a different set. 
 66
 67define function convert($x) { 
 68
 69typeswitch ($x) 
 70
 71case element para return <p>{process-children($x)}</p>
 72
 73case element emph  return <em>{process-children($x)}</em>
 74
 75default return process-children($x) 
 76
 77} 
 78
 79define function process-children($x) { 
 80
 81for $ch in children($x) 
 82
 83return convert($ch) 
 84
 85} 
 86
 87Hello, 
 88
 89I am a beginner in Xquery. 
 90
 91In my schema I have element which has IDREF attribute.I want to extract id value to which points and check whether that value is equivalent to some value. 
 92
 93eg: 
 94
 95<author emailid="[email protected]">
 96<fname>smith</fname>
 97<mi>j</mi>
 98<lname>jen</lname>
 99</author>
100<paper emailid="[email protected]" paperid="10">
101<mainathr>SHARMA</mainathr>
102<title>ABC</title>
103</paper>
104<paper emailid="[email protected]" paperid="10">
105<mainathr>SHARMA</mainathr>
106<title>ABC</title>
107</paper>
108
109let $id := "[email protected]", 
110
111for $paper in $doc/PAPER[@EMAILID = $id], 
112
113for $author in $doc/AUTHOR[@EMAILID = $id] 
114
115return 
116
117<result paperid="{$paper/@PAPERID}">
118
119{$author/FNAME} 
120
121<result>
122
123for $paper in $doc/PAPER, 
124
125for $author in $doc/AUTHOR 
126
127where $paper/@EMAILID = $auther/$EMAILID 
128
129return 
130
131<result paperid="{$paper/@PAPERID}">
132
133{$author/FNAME} 
134
135<result>
136
137如上例程序，在  xquery  中引用节点和节点属性名称的时候稍有不同。 
138
139节点  paper  属性  @paper 
140
141I am completely new to XQuery.. 
142
143I have the following which I would like to run on an .xml file... 
144
145for $book in bib.xml//book 
146
147let $title := $book/title 
148
149where $book/publisher = 'Addison-Wesley' 
150
151return 
152
153<bookinfo>
154
155{ $title } 
156
157</bookinfo>
158
159and the bib.xml file 
160
161<bib>
162<book year="1994">
163<title>TCP/IP Illustrated</title>
164<author><last>Stevens</last><first>W.</first></author>
165<publisher>Addison-Wesley</publisher>
166<price> 65.95</price>
167</book>
168<book year="1992">
169<title>Advanced Programming in the Unix environment</title>
170<author><last>Stevens</last><first>W.</first></author>
171<publisher>Addison-Wesley</publisher>
172<price>65.95</price>
173</book>
174<book year="2000">
175<title>Data on the Web</title>
176<author><last>Abiteboul</last><first>Serge</first></author>
177<author><last>Buneman</last><first>Peter</first></author>
178<author><last>Suciu</last><first>Dan</first></author>
179<publisher>Morgan Kaufmann Publishers</publisher>
180<price>39.95</price>
181</book>
182<book year="1999">
183<title>The Economics of Technology and Content for Digital TV</title>
184<editor>
185<last>Gerbarg</last><first>Darcy</first>
186<affiliation>CITI</affiliation>
187</editor>
188<publisher>Kluwer Academic Publishers</publisher>
189<price>129.95</price>
190</book>
191</bib>
192
193\----------------------------------------------- 
194
195最后附上一个好的教材： 
196
197**http://monetdb.cwi.nl/XQuery/Demo/index.html**   
198**http://www.xml.com/pub/a/2005/03/02/xquery.html**   
199**http://www.xml.com/pub/a/2005/03/23/xquery-2.html**   
200**http://www.w3schools.com/xquery/default.asp**   
201
202
203Copyright@ ♂猜猜♂. 2005. All rights reserved</result></result></result></result></greeting>

eXist Xquery Examples

eXist Xquery Examples

** [ 基础操作 ] **

[ 函数的定义与调用 ]

[ 节点和节点类型 ]

[flwor 表达式 / 数据库检索命令 ]

[ 数量操作 ] 该操作非常有用该操作非常有用

[xpath 例子 ]

[ 基础操作 ]