XPath syntax quick check

The specific learning of XPath can be viewed through the viewing (link: http://www.w3school.com.cn/xpath/index.asp)

Here is just the usual use of a few tables posted, later query:

Here's the XPath I personally feel like selectors that have

syntax +XPath axis operation + operator + function

Several combinations are used.

A lot of functions, do not post out, need to be able to search by the information: http://www.w3school.com.cn/xpath/xpath_functions.asp

XPath Syntax Selection node

XPath uses a path expression to select a node in the XML document. A node is selected by a path or step.

The most useful path expressions are listed below:

An expression	Description
NodeName	Select all child nodes of this node.
/	Select from the root node.
//	Selects the nodes in the document from the current node that matches the selection, regardless of their location.
.	Select the current node.
..	Selects the parent node of the current node.
@	Select the attribute.

Instance

In the table below, we have listed some path expressions and the results of the expressions:

Path Expression	Results
Bookstore	Selects all child nodes of the bookstore element.
/bookstore	Select the root element bookstore. Note: If the path starts with a forward slash (/), this path always represents the absolute path to an element!
Bookstore/book	Selects all book elements that belong to a child element of bookstore.
Book	Selects all book child elements, regardless of their position in the document.
Bookstore//book	Selects all book elements that belong to descendants of the bookstore element, regardless of where they are located under bookstore.
@lang	Select all attributes that are named Lang.

predicate (predicates)

To find a particular node or a node that contains a specified value.

The predicate is embedded in square brackets.

Instance

In the table below, we list some path expressions with predicates, as well as the results of expressions:

Path Expression	Results
/BOOKSTORE/BOOK[1]	Selects the first book element that belongs to a bookstore child element.
/bookstore/book[last ()]	Select the last book element that belongs to the bookstore child element.
/bookstore/book[last ()-1]	Select the second-to-last book element that belongs to the bookstore child element.
/bookstore/book[position () <3]	Select the first two book element that belongs to the child element of the bookstore element.
title[@lang]	Select all the title elements that have properties named Lang.
title[@lang = ' Eng ']	Selects all title elements, and these elements have the lang attribute value of Eng.
/BOOKSTORE/BOOK[PRICE>35.00]	Selects all the book elements of the bookstore element, and the value of the price element must be greater than 35.00.
/bookstore/book[price>35.00]/title	Selects all the title elements of the book element in the bookstore element, and the value of the price element must be greater than 35.00.

Select Unknown node

XPath wildcard characters can be used to select unknown XML elements.

wildcard characters	Description
*	Matches any element node.
@*	matches any attribute node.
Node ()	Matches any type of node.

Instance

In the table below, we list some path expressions and the results of these expressions:

Path Expression	Results
/bookstore/*	Selects all child elements of the bookstore element.
//*	Selects all elements in the document.
Title[@*]	Select all the title elements with attributes.

Select several paths

By using the ' | ' in a path expression operator, you can select a number of paths.

Instance

In the table below, we list some path expressions and the results of these expressions:

Path Expression	Results
Book/title | Book/price	Selects all the title and price elements of the book element.
Title | Price	Selects all the title and price elements in the document.
/bookstore/book/title | Price	Selects all the title elements of the book element that belong to the bookstore element, and all the price elements in the document.

XPath Axes (axis) XPath axis

An axis defines a set of nodes relative to the current node.

Axis name	Results
Ancestor	Selects all ancestors of the current node (parent, grandfather, etc.).
Ancestor-or-self	Selects all ancestors of the current node (parent, grandfather, etc.) and the current node itself.
Attribute	Selects all the properties of the current node.
Child	Selects all child elements of the current node.
Descendant	Selects all descendant elements (child, grandchild, and so on) of the current node.
Descendant-or-self	Selects all descendant elements (child, grandchild, and so on) of the current node and the current node itself.
Following	Selects all nodes after the end tag of the current node in the document.
Namespace	Selects all the namespace nodes of the current node.
Parent	Selects the parent node of the current node.
Preceding	Selects all nodes before the start tag of the current node in the document.
Preceding-sibling	Selects all sibling nodes before the current node.
Self	Select the current node.

Position path expression

The location path can be absolute, or it can be relative.

The absolute path starts with a forward slash (/), and the relative path does not. In both cases, the location path consists of one or more steps, each of which is split by a slash:

Absolute location Path:

/step/step/...

Relative position path:

step/step/...

Each step is calculated based on the nodes in the current node set.

Step includes:

Axes (axis)

Defines the tree relationship between the selected node and the current node

Node Test (node-test)

Identify the nodes inside an axis

0 or more predicates (predicate)

refine the selected node set in more

detail

Syntax of the step:

Axis Name:: node test [predicate]

Instance

Example	Results
Child::book	Select all the book nodes that belong to the child elements of the current node.
Attribute::lang	Select the Lang property of the current node.
Child::*	Selects all child elements of the current node.
Attribute::*	Selects all the properties of the current node.
Child::text ()	Selects all the text child nodes of the current node.
Child::node ()	Selects all child nodes of the current node.
Descendant::book	Selects all book descendants of the current node.
Ancestor::book	Selects all the book ancestors of the current node.
Ancestor-or-self::book	Selects all the book ancestors of the current node and the current node (if this node is a book node)
Child::*/child::p	Selects all the price sun nodes of the current node.

XPath operator XPath operator

The following lists the operators that are available in XPath expressions:

operator	Description	Example	return value
|	Compute two node sets	Book | Cd	Returns all node sets that have book and CD elements
+	Addition	6 + 4	10
-	Subtraction	6-4	2
*	Multiplication	6 * 4	24
Div	Division	8 Div 4	2
=	Equals	price=9.80	Returns true if Price is 9.80. If Price is 9.90, False is returned.
!=	Not equal to	price!=9.80	Returns true if Price is 9.90. If Price is 9.80, False is returned.
<	Less than	price<9.80	Returns true if Price is 9.00. If Price is 9.90, False is returned.
<=	Less than or equal to	price<=9.80	Returns true if Price is 9.00. If Price is 9.90, False is returned.
>	Greater than	price>9.80	Returns true if Price is 9.90. If Price is 9.80, False is returned.
>=	Greater than or equal to	price>=9.80	Returns true if Price is 9.90. If Price is 9.70, False is returned.
Or	Or	price=9.80 or price=9.70	Returns true if Price is 9.80. If Price is 9.50, False is returned.
and	And	price>9.00 and price<9.90	Returns true if Price is 9.80. If Price is 8.50, False is returned.
MoD	Calculate the remainder of a division	5 MoD 2	1

XPath syntax quick check