Esper EQL 检查属性是否设置

Question

假设我们有以下语句：

String STATEMENT =
            "SELECT" +
                    " l.address.locality," +
            " FROM" +
                    " Location AS l";

现在地址可能是空的。在这种情况下，我如何告诉 Esper 不要通知我的订阅者？

Answer 1

SELECT address.locality FROM Location(address is not null)

Esper EQL check if attribute is set