Row triggers cannot designate an identifier for a transition table and statement triggers cannot designate a correlation for transition variables.
An update that sets a column value to the value that it originally contained (for example, UPDATE T SET C = C) causes a row trigger to fire, even though the value of the column is the same as it was prior to the triggering event.
When we retrieve that column, the query does not return the updated column values, but other columns are being updated and we are able to see those values. It happens more often than you might think, in real life.) I looked at their trigger and decided immediately that I did not like it.
Along with constraints, triggers can help enforce data integrity rules with actions such as cascading deletes or updates.
The triggered-SQL-statement can reference database objects other than the table upon which the trigger is declared.
If any of these database objects is dropped, the trigger is invalidated.
A trigger is just like a subroutine , but most people consider triggers part of the DDL.
And just as you would not review a CREATE TABLE statement while reviewing a package implementation, most people do not review the hidden code in a trigger.