oracle触发器语法和实例（Oracle triggers syntax and examples）.docVIP

oracle触发器语法和实例（Oracle triggers syntax and examples） Oracle trigger syntax (1) A Oracle trigger syntax A trigger is a block of code that is automatically executed when a particular event occurs. Similar to a stored procedure, the difference between a trigger and a stored procedure is that the stored procedure is explicitly invoked by the user or application, and the trigger cannot be called directly. Function: 1 allow / restrict modifications to the watch 2, automatically generate derived columns, such as self increasing fields 3, mandatory data consistency 4 provide audit and log records 5, prevent invalid transaction processing 6, enable complex business logic There are two triggers for trigger time: after and before. 1, the syntax of triggers: CREATE, [OR, REPLACE], TIGGER, trigger name, trigger time, trigger event ON table name [FOR EACH ROW] BEGIN Pl/sql statement END Among them: Trigger name: the name of the trigger object. Since the trigger is automatically executed by the database, the name is only a name and has no real use. Trigger time: indicates when the trigger is executed. This value is desirable: Before--- indicates that the trigger executes before the database action; After--- indicates that the boot executes after the database action. Trigger event: indicates which database actions will trigger the trigger: Insert: database insert triggers this trigger; Oracle trigger syntax (two) Update: database modification triggers this trigger; Delete: database deletion triggers this trigger. Table name: the table where the database triggers are located. For each row: execution of each row trigger on the table. If this option is not available, the entire table is executed only once. 2, for example: The following triggers are triggered before the table auths is updated, so that the table is not allowed to change at the weekend: Create triggerauth_secure before insert or update or delete on the table before the update trigger / / On auths Begin If (to_char (sysdat