For details, see "Correlation Names and Pseudorecords". With a column list, the trigger fires only when a specified column is updated.Without a column list, the trigger fires when any column of the associated table is updated.Like a stored procedure, a trigger is a named PL/SQL unit that is stored in the database and can be invoked repeatedly.
Therefore, do not create triggers that depend on the order in which rows are processed.
For example, do not assign a value to a global package variable in a row trigger if the current value of the global variable is dependent on the row being processed by the row trigger.
For example, a table and a trigger can have the same name (however, to avoid confusion, this is not recommended).
A trigger is fired based on a triggering statement, which specifies: statement might include a list of columns.
Once the trigger is created, entering the following SQL statement: A trigger is either a stored PL/SQL block or a PL/SQL, C, or Java procedure associated with a table, view, schema, or the database itself.
Oracle Database automatically executes a trigger when a specified event takes place, which may be in the form of a system event or a DML statement being issued against the table.A column list cannot be specified for statement trigger is fired again.The rollback to savepoint does not undo changes to any package variables referenced in the trigger.If a triggering statement includes a column list, the trigger is fired only when one of the specified columns is updated.If a triggering statement omits a column list, the trigger is fired when any column of the associated table is updated.PUT_LINE('Difference: '