XQuery misoli
Keling, bir misolni ko‘rib chiqib, XQuery asoslarini o‘rganamiz.
Misol uchun XML hujjat
Quyidagi misollarda biz quyidagi XML hujjatdan foydalanamiz.
"books.xml":
<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
<book category="WEB">
<title lang="en">XQuery Kick Start</title>
<author>James McGovern</author>
<author>Per Bothner</author>
<author>Kurt Cagle</author>
<author>James Linn</author>
<author>Vaidyanathan Nagarajan</author>
<year>2003</year>
<price>49.99</price>
</book>
<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>39.95</price>
</book>
</bookstore>"books.xml" faylini brauzeringizda ko‘ring.
"books.xml" faylidan tugunlarni qanday tanlash mumkin?
Funksiyalar
XQuery XML hujjatlardan ma’lumot ajratib olish uchun funksiyalardan foydalanadi.
"books.xml" faylini ochish uchun doc() funksiyasidan foydalaniladi:
doc("books.xml")Yo‘l ifodalari (path expressions)
XQuery XML hujjatdagi elementlar bo‘ylab harakatlanish uchun yo‘l ifodalaridan foydalanadi.
Quyidagi yo‘l ifodasi "books.xml" faylidagi barcha title elementlarini tanlash uchun ishlatiladi:
doc("books.xml")/bookstore/book/title(/bookstore bookstore elementini tanlaydi, /book bookstore elementi ostidagi barcha book elementlarini tanlaydi, /title esa har bir book elementi ostidagi barcha title elementlarini tanlaydi)
Yuqoridagi XQuery quyidagilarni ajratib oladi:
<title lang="en">Everyday Italian</title>
<title lang="en">Harry Potter</title>
<title lang="en">XQuery Kick Start</title>
<title lang="en">Learning XML</title>Predikatlar
XQuery XML hujjatlardan ajratib olinadigan ma’lumotlarni cheklash uchun predikatlardan foydalanadi.
Quyidagi predikat bookstore elementi ostidagi, qiymati 30 dan kichik bo‘lgan price elementiga ega barcha book elementlarini tanlash uchun ishlatiladi:
doc("books.xml")/bookstore/book[price<30]Yuqoridagi XQuery quyidagilarni ajratib oladi:
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>W3Schools Pathfinder
Yutuqlaringizni kuzating – bu bepul!