Although e-commerce is becoming popular, product rules, which describe various conditions such as prices, applicability, and discount conditions are still expressed in natural languages. These rules are difficult to deal with in relational databases because logics are separated from data. There is no system to search on multiple rules, so buyers have to check business rules one by one. In this paper, we take the case of airline tickets, hotel bookings and others as an example, and describe them in dynamic constraint conditions. We also show several queries written in Dynamic Constraint Algebra (DCA), and the result of the Dynamic Constraint Algebra Query Processing Engine can be utilized to present buyers available options, and to check how variables affect prices.