How to generate query based off from user input

Sorry, I know its hairy -

but if customer_id has a value, I want it injected into filter, and the filter used, e.g.

        var(func:eq(customer_id, "10000000000"))

if customer_id is not set by the client (and because its an int, will have a default value of 0) - i dont want the filter to run.

so if ehid is “1” and customer_id not set, i want xcode to be x3

@include looks like it would have helped