IS420chapter16(Triggers)
How does a mutation error occur?
It occurs If the trigger body tries to directly read/update the current table
Trigger action
PL/SQL code that is executed
What is the action of the trigger?
PL/SQL code that will be automatically executed (fired) when the trigger fires
New
stores values after the modification
Old
stores values before the modification
Statement Level trigger
- Trigger fires ONCE per event (default)
Row level trigger
- Trigger fires for each row affected by the event
What happens when a trigger fires?
- all operations performed become part of the transaction of a SQL statement that caused the trigger to fire
Trigger event
- associated with the INSERT, UPDATE, or DELETE operations performed on the trigger table
Trigger timing
- before or after the event - The time when the execution of the trigger will occur
Before Timing
- implies that the trigger will be fired prior to the completion of the database event
Trigger levels
- scope affected by the trigger
Trigger
- specification of database event associated with a database table
After timing
- timing implies that the trigger will be fired after the actual database event
What statements cause triggers to fire?
-INSERT,UPDATE,DELETE
What can triggers not do?
They cannot accept input parameters, commit or rollback statements
How is a trigger executed?
They`re fired in response to database events