Uchaguzi na Uchaguzi wa XQuery

Andiko la mbinu ya XML

Tunatengenezwa kwa mifano hivi kwa andiko la "books.xml" (na andiko la XML iliyotumiwa kwenye majadiliano yaliyopita).

在您的浏览器中查看 "books.xml" 文件。

选择和过滤元素

正如在前面的章节所看到的，我们使用路径表达式或 FLWOR 表达式来选取和过滤元素。

请看下面的 FLWOR 表达式：

for $x in doc("books.xml")/bookstore/book
where $x/price>30
order by $x/title
return $x/title
for
（可选） 向每个由 in 表达式返回的项目捆绑一个变量
let
(chaguo)
where
(chaguo) Inaaminika shida
order by
(chaguo) Inaaminika ujenzi wa matokeo
rua
Inaaminika ujenzi wa matokeo

Sentenja for

Sentenja for inaweza kubinda kina kina cha kina cha in kwa kubinda kina kina cha in. Sentenja for inaweza kubainisha mchakato wa kina kina. Inaweza kuwa na sentenja for kina kina cha in kwenye mchakato wa FLWOR.

Kwa kufikia matokeo ya kipindi cha in kwa kumtaarifu ngumu, inaweza kutumika:Kichwa cha kingine cha kutoka : 

for $x in (1 kutoka 5)
return {$x}

Matokeo: 

<test>1</test>
<test>2</test>
<test>3</test>
<test>4</test>
<test>5</test>

Kichwa cha kingine cha at Inaweza kutumika kuongeza matokeo ya mchakato:

for $x katika $i in doc("books.xml")/bookstore/book/title
rua <book>{$i}. {data($x)}</book>

Matokeo:

<book>1. Italiani ya Kila Siku</book>
<book>2. Harry Potter</book>
<book>3. Inasikia XQuery Kick Start</book>
<book>4. Kujifunza XML</book>

Inafanana na kipindi cha in kwa sentenja forInaweza kuwa na mabaghalasho mengi ya inTumia kombo la kipindi cha in kuingia kwa kufungua kipindi cha in:

for $x in (10,20), $y in (100,200)
rua <test>x={$x} na y={$y}</test>

Matokeo:

<test>x=10 na y=100</test>
<test>x=10 na y=200</test>
<test>x=20 na y=100</test>
<test>x=20 na y=200</test>

let sentenja

let 语句可完成变量分配，并可避免多次重复相同的表达式。let 语句不会导致迭代。

let $x := (1 to 5)
return {$x}

Matokeo:

1 2 3 4 5

where 语句

where 语句用于为结果设定一个或多个条件（criteria）。

where $x/price>30 and $x/price<100

order by 语句

order by 语句用于规定结果的排序次序。在这里，我们要根据 category 和 title 来对结果进行排序：

for $x in doc("books.xml")/bookstore/book
order by $x/@category, $x/title
return $x/title

Matokeo:

<title lang="en">Harry Potter</title>
<title lang="en">Italiani ya Kila Siku</title>
<title lang="en">Mafunzo ya XML</title>
<title lang="en">Inagawa wa XQuery</title>

Kamuo wa return:

Kamuo wa return inasababisha kufikia matokeo ya kufikia.

for $x in doc("books.xml")/bookstore/book
return $x/title

Matokeo:

<title lang="en">Italiani ya Kila Siku</title>
<title lang="en">Harry Potter</title>
<title lang="en">Inagawa wa XQuery</title>
<title lang="en">Mafunzo ya XML</title>