XQuery Expression learning

open the file: doc("xxx.xml")

 

doc("xxx.xml")/bookstore/book[conditon clause]

 

for, where, order, return

 

doc("xxx.xml")/bookstore/book[price>20]/title

=

for $x in doc("xxx.xml")/bookstore/book

where $x/price>20

order by $x/title

return $x/title

 

integrate with html tags

<ul>

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

oder by $x

return <li>($x)</li>

</ul> 

 

get the data directly use the data() function

ex:

<ul>

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

return <li>(data|($x))</li>

</ul>

 

basic syntax rules

comment: (:  I am comment :)

"if-then-else": 

for $x in doc("xxx.xml")/bookstore/book

return if ($x/@attribute="hey")

then <child>(data($x/title))</child>

else <adult>(data($x/title))<adult>

comparisons:

one group: =, !=, <, <=, >, >=

another group: eq, ne, lt, le, gt, ge

what's the difference? see the follow two examples

$bookstore//book/@q > 20   --> if any items fulfill the condition,  then return true

$bookstore//book/@q lt 20   --> only one item fulfill the condition, then return true

 

use function

default functions: upper-case, substring, data, and so on...

custom function:

declare function prefix:function_name($parameter AS datatype)

AS returnDataType{

  ...

}