Vertica doesn't support triggers. This may seem strange if you're coming from another database platform, but the fact is Vertica was designed for analytical reporting applications, while triggers are more about transaction processing.
It is my impression that most Vertica users (including my company) process transactional updates to data in a more traditional Relation Database or other system and periodically batch-load Vertica with any updates. Any business rules or data validation requiring a trigger or other procedural logic should occur on this other, primary database system.