Getting Started with DB2 Express-C

268 Getting Started with DB2 Express-C
A quick way to learn XPath is to compare it to the change directory (cd) command
in MS-DOS or Linux/UNIX. Using the cd command, you traverse a directory tree as
follows:
cd /directory1/directory2/…
Similarly, in XPath you use slashes to go from one element to another within the XML
document. For example, using the document in Listing 15.1 in XPath you could retrieve
the names of all employees using this query:
/dept/employee/name
15.3.2.1 XPath expressions
XPath expressions use fully qualified paths to specify elements and attributes. An “@” sign
is used to specify an attribute. To retrieve only the value (text node) of an element, use the
text() function. Table 15.2 shows XPath queries and the corresponding results using the
XML document from Listing 15.1.
XPath
Result
/dept/@bldg 101
/dept/employee/@id 901
902
/dept/employee/name
/dept/employee/name/text()
Peter Pan
John Doe
Peter Pan
John Doe
Table 15.2 – XPath expression examples
15.3.2.2 XPath wildcards
There are two main wildcards in XPath:
• “*” matches any tag name
• “//” is the “descendent-or-self” wildcard
Table 15.3 provides more examples using the XML document from Listing 15.1
XPath
Result
/dept/employee/*/text()
John Doe
408 555 1212
344
Peter Pan