there is at most one <object>

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there is at most one <object>

Summary

Tests to see if there is no more than one object of a given type in the current data set or the specified collection.

Syntax

there is at most one <object> [in <list>] [where <test>,*]

Description

Use this construct to determine if the current data set contains zero or one occurrences of a particular object.

Use the optional in clause to apply the test to a specific collection of objects. Use one or more optional where clauses to filter the objects to be counted with one or more conditions.

This construct can only be used in the if part of a rule.

Example

The following condition tests if there is at most one Gold customer in the set of objects provided to the rule engine for execution.

if
   there is at most one customer
      where the category of this customer is Gold,
then...