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Version: Java (Groovy)

Use the ternary conditional operator in query strings

This guide will show you how to use the ternary conditional operator, also known as ternary-if, in query strings. The ternary conditional operator evaluates a boolean expression and returns the result of one of two expressions, depending on whether the boolean expression evaluates to true or false. The operator is similar to an inline if-then-else code block.

Ternary conditional operator (ternary-if)​

The syntax for the ternary conditional operator is: condition ? expressionIfTrue : expressionIfFalse

The question mark (?) separates the condition from the expressions, and the colon (:) separates the expression evaluated when the condition is true from the expression evaluated when the condition is false.

The expression x ? y : z evaluates as follows:

  • If x is true, the expression evaluates to y.
  • If x is false, the expression evaluates to z.

The expression x ? (y ? 1 : 2) : 3 evaluates as follows:

  • If both x and y are true, the expression evaluates to 1.
  • If x is true, and y is false, the expression evaluates to 2.
  • If x is false, the expression evaluates to 3.

Example​

A home builder has a budget of $3.50/board-foot to purchase lumber and would like to know what types of wood are within their budget. We can use the ternary operator to create a new table with a "yes" or "no" column that answers if a wood type is within the budget constraints.

woods = newTable(
    stringCol("Type", "Pine", "Fir", "Cedar", "Oak", "Ash", "Walnut", "Beech", "Cherry"),
    stringCol("Hardness", "soft", "soft", "soft", "hard", "hard", "hard", "hard", "hard"),
    doubleCol("Price", 1.95, 2.50, 3.25, 3.45, 4.25, 7.95 , 4.10, 5.25)
)

result = woods.update("Budget = (Price<=3.50) ? `yes` : `no` ")

Nested ternary conditional operators​

For more complex cases with multiple conditions, ternary-if statements can be nested. For example:

condition1 ? (condition2 ? value1 : value2) : value3

The expression x ? (y ? 1 : 2) : 3 evaluates as follows:

  • If both x and y are true, the expression evaluates to 1.
  • If x is true, and y is false, the expression evaluates to 2.
  • If x is false, the expression evaluates to 3.

Example​

A home builder has a budget of $3.50/board-foot to purchase hardwood lumber and would like to know what types of wood are within their budget. We can use nested ternary operators to create a new table with a yes or no column that answers if a wood type is both within the budget constraints and a hardwood.

In this example, the Possible column evaluates to yes only if the wood is both hardwood and the price is less than $3.50. Otherwise, the wood is not offered as a possibility for the customer.

result = woods.update("Possible = (Hardness == `hard`) ? ( (Price <= 3.50) ? `yes` : `no` ) : `no` ")

If hardwood is a requirement but the budget is flexible, nested ternary-ifs can be used to categorize hardwoods as budget or expensive and all other wood types as no. This is seen below:

result = woods.update("possible = (Hardness == `hard`) ? ( (Price <= 3.50) ? `budget` : `expensive` ) : `no` ")

Using a custom method​

Using a custom method in a ternary statement is very straightforward. All you need to do is replace the condition with your method call. However, there's a catch - you need to cast the method call to (Boolean).

The following example shows how to use a custom method in a ternary statement.

budget = { price ->
    return price <= 3.50
}

woods = newTable(
    stringCol("Type", "Pine", "Fir", "Cedar", "Oak", "Ash", "Walnut", "Beech", "Cherry"),
    stringCol("Hardness", "soft", "soft", "soft", "hard", "hard", "hard", "hard", "hard"),
    doubleCol("Price", 1.95, 2.50, 3.25, 3.45, 4.25, 7.95 , 4.10, 5.25)
)

result = woods.update("Budget = (Boolean)budget(Price) ? `yes` : `no` ")

Create a new table