XQuery If Then Else

In XQuery, the if-then-else expression is used for conditional branching, similar to other programming languages. It allows you to evaluate a condition, and based on the result, perform different actions. The basic syntax of the if-then-else expression in XQuery is as follows:

if (condition) then
  expression1
else
  expression2

• condition: The condition that is evaluated. It should result in a boolean value (true or false).
• expression1: The expression that is executed when the condition is true.
• expression2: The expression that is executed when the condition is false.

The if-then-else expression can be used as part of an XQuery FLWOR expression or within other XQuery constructs.

Example 1:

let $x := 10
return if ($x > 5) then
  "Greater than 5"
else
  "Less than or equal to 5"

Output: “Greater than 5”

In this example, the condition $x > 5 is true since the value of $x is 10. Therefore, the result of the if-then-else expression is “Greater than 5”.

Example 2:

let $fruit := "apple"
return
  if ($fruit eq "apple") then
    "It's an apple."
  else if ($fruit eq "orange") then
    "It's an orange."
  else
    "It's something else."

Output: “It’s an apple.”

In this example, the condition $fruit eq "apple" is true, so the first branch is executed, and the result is “It’s an apple.”

You can nest if-then-else expressions to handle multiple conditions. The expressions are evaluated sequentially, and the first true condition’s corresponding expression is executed. If none of the conditions is true, the else expression (if provided) or nothing will be executed.

if-then-else expressions are valuable for making decisions and controlling the flow of XQuery queries based on specific conditions in the data being processed.