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The [https://en.wikipedia.org/wiki/%3F : ternary if] operator provides a short syntax for conditions. It is also called '''conditional operator''' or '''ternary operator'''. In most languages , the syntax is <code>a ? b : c</code>. As <code>?</code> and <code>:</code> have already been taken in XQuery, the syntax of Perl 6 syntax is used:

The Elvis operator returns is also available in other languages. It is sometimes called [https://en.wikipedia.org/wiki/Null_coalescing_operator null-coalescing operator]. In XQuery, the value of the first operand will be returned if it’s it is a non-empty sequence. Otherwise, or the value of the second operand otherwise:will be returned.

let $number := 123return ( (: if/then/else :) if (exists($number)) then $number else 0, (: elvis operator :) $number ?: 0)

It The behavior of the operator is equivalent to the {{Function|Utility|util:or}} function.

In the XQuery standard3.1, both branches of the <code>if</code> expression need to be specified. As in In many cases, only one branch is required, so the <code>else</code> branch is was made optional in BaseX. If the second branch is omitted, an empty sequence is will be returned if the effective boolean value of the test expression is false. Some examples:

If the expression is conditions are nested, a trailing else branch is will be associated with the innermost <code>if</code>. As in other languages: <pre class="brush:xquery">if ($a) then if($b) then '$a and $b is true' else 'only $b is true'</pre> In general, it is recommendable to use if you have multiple or nested if expressions, additional parentheses to make a query better readablecan improve the readibility of your code:

if($b) then 'c$a and $b is true' else 'donly $b is true'