A stored procedure is a set of SQL commands that can be compiled and stored in the server. Once this
has been done, clients don't need to keep reissuing the entire query but can refer to the stored
procedure. This provides better performance because the query has to be parsed only once, and less
information needs to be sent between the server and the client. You can also raise the conceptual level
by having libraries of functions in the server.
A trigger is a stored procedure that is invoked when a particular event occurs. For example, you can
install a stored procedure that is triggered each time a record is deleted from a transaction table and that
automatically deletes the corresponding customer from a customer table when all his transactions are
deleted.
The planned update language will be able to handle stored procedures, but without triggers. Triggers
usually slow down everything, even queries for which they are not needed.