XQuery is case-sensitive and XQuery elements, attributes, and variables must be valid XML names.
Some basic syntax rules:
We will use the "books.xml" document in the examples below (same XML file as in the previous chapters).
"If-Then-Else" expressions are allowed in XQuery.
Look at the following example:
Notes on the "if-then-else" syntax: parentheses around the if expression are required. else is required, but it can be just else ().
The result of the example above will be:
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:
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: