Oracle sql trigger if updating review best software for automatically updating drivers
A trigger is a named PL/SQL block stored in the Oracle Database and executed automatically when a triggering event takes place.
By default, a trigger is created in the enabled state. When a trigger fires, tables that the trigger references might be undergoing changes made by SQL statements in other users' transactions.SQL statements running in triggers follow the same rules that standalone SQL statements do.Specifically: How Triggers and Constraints Differ Both triggers and constraints can constrain data input, but they differ significantly. For example, a trigger can prevent a DML statement from inserting a values that were inserted into the column before the trigger was defined or while the trigger was disabled.Many applications update all of the columns in a table -- setting them to their old value, rather then trying to figure out exactly which columns have been updated by the client. Let's look at a simple example: create or replace trigger test_trigger 2 after update of x,y on test 3 for each row 4 begin 5 if updating( 'X' ) then 6 dbms_output.put_line( 'X is being updated' ); 7 end if; 8 9 if updating( 'Y' ) then 10 dbms_output.put_line( 'Y is being updated' ); 11 end if; 12 end; 13 / Trigger created. You can use updating (column) but it will only tell you that the column itself is being updated and not if the value has changed.
If you need to determine if the value is changing, you'll still need to code comparison logic for :old and :new values.A statement-trigger fire once regardless of the number of rows affected by the triggering event.