Changed data can be referred to in the triggered-SQL-statement using serve as a table identifier for the triggered-SQL-statement or the trigger qualification.The referencing clause allows you to provide a correlation name or alias for these transition tables by specifying OLD_TABLE/NEW_TABLE AS correlation-Name Only statement triggers (see Statement versus row triggers) can use the transition tables.
The triggered-SQL-statement might need to refer to the new (post-change or "after") values.
provides you with a number of ways to refer to data that is currently being changed by the database event that caused the trigger to fire.
Along with constraints, triggers can help enforce data integrity rules with actions such as cascading deletes or updates.
Triggers can also perform a variety of functions such as issuing alerts, updating other tables, sending e-mail, and other useful actions.
Does anyone have an example or better suggestion on how to improve this?
For example, if you define a trigger for a delete on a particular table, the trigger's action occurs whenever someone deletes a row or rows from the table.
The referencing clause can designate only one new correlation or identifier and only one old correlation or identifier.
Row triggers cannot designate an identifier for a transition table and statement triggers cannot designate a correlation for transition variables.
Also, for a DML trigger it is mandatory to specify the event phase and the name of the table or view that is to “ Altering the status, phase, table or view event(s), firing position and code in the body of a DML trigger are all possible.
However, you cannot modify a DML trigger to convert it to a database trigger, nor vice versa.
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.