XQuery Conditional Expressions and Comparisons

"If-Then-Else" expressions,

example:

for $x in doc("books.xml")/bookstore/book
return if ($x/@category="CHILDREN")
then <child>{data($x/title)}</child>

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

Comparisons

In XQuery there are two ways of comparing values.

1. General comparisons: =, !=, <, <=, >, >=

2. Value comparisons: eq, ne, lt, le, gt, ge

The difference between the two comparison methods are shown below.

The following expression returns true if any q attributes have a value greater than 10:

$bookstore//book/@q > 10

The following expression returns true if there is only one q attribute returned by the expression, and its value is greater than 10. If more than one q is returned, an error occurs:


$bookstore//book/@q gt 10