TBE: Trigger-By-Example

Triggers have been adopted as an important database feature and implemented by most major database vendors. Despite their diverse potential usages, one of the obstacles that hinder the triggers from its wide deployment is the lack of tools that aid users to create complex trigger rules in a simple manner. Although the majority of the users of triggers are DBAs or savvy end-users, writing trigger rules is still a daunting task. On the other hand, QBE (Query-By-Example) has been very popular as a user interface for creating queries in an interactive and intuitive manner since its introduction decades ago. It is being used in most modern database products in its disguised form. Since its underlying theory is based on the relational calculus, its expressive power is proved to be equivalent to that of SQL. Therefore, it is an ideal tool for novice users to create simple queries in visual fashion. At the same time, expert users do not have to compromise anything because QBE supports full capability to create complex queries. In this paper, we shall present a novel user interface for creating trigger rules, called TBE (TriggerBy-Example), by marrying the triggers and QBE in a seamless fashion. The visual nature of the TBE makes writing trigger rules much easier. We show how trigger rules in the emerging SQL standard (SQL3) can be represented using the TBE with minimal introduction of new constructs. Further, an algorithm to translate from the TBE to SQL3 triggers is developed and illustrated along with examples. Finally, a preliminary implementation of the TBE is presented as a proof of the concept.