Let's talk about the modification operation of oracle triggers

Oracle trigger is a special type of database object that can listen to certain events in the database and automatically perform specified operations after these events occur. Triggers can be used to realize automatic management of the database, data consistency maintenance, data security guarantee and other purposes. In this article, we will focus on the modification operation of Oracle triggers.

In Oracle database, triggers can be divided into two categories: row-level triggers and statement-level triggers. Row-level triggers are triggered based on changes in row data, that is, for each inserted, updated, or deleted row, the execution of the trigger is triggered. The statement-level trigger is triggered based on the execution of the operation statement, that is, for each operation statement that executes the trigger, the execution of the trigger will be triggered once.

Modify row-level triggers

The following is an example of modifying a row-level trigger:

CREATE OR REPLACE TRIGGER trig1
AFTER INSERT ON my_table
FOR EACH ROW
BEGIN
  -- do something here
END;

This trigger is defined on the my_table table, and it will be used every time Automatically executed every time a new record is inserted into the table. Now assuming that we need to modify the execution content of this trigger, we can follow the following steps:

1. Delete the original trigger first:

DROP TRIGGER trig1;

2. As required Redefine the trigger:

CREATE OR REPLACE TRIGGER trig1
AFTER INSERT ON my_table
FOR EACH ROW
BEGIN
  -- do something new here
END;

CREATE OR REPLACE here means that if the trigger named trig1 already exists, overwrite it; otherwise, create a new trig1 trigger . In this example, we only modified the execution statement in the trigger body, leaving the other parts unchanged.

In this way, we can easily modify the execution process of any row-level trigger.

Modify statement-level triggers

The following is an example of a statement-level trigger:

CREATE OR REPLACE TRIGGER trig2
AFTER INSERT ON my_table
BEGIN
  -- do something here
END;

This trigger defines the operation to be performed after inserting a record into the my_table table . If we need to perform this operation after deleting the record, we can modify the trigger to:

CREATE OR REPLACE TRIGGER trig2
AFTER INSERT OR DELETE ON my_table
BEGIN
  -- do something here
END;

The modification here is to change the event type from AFTER INSERT to AFTER INSERT OR DELETE means that the trigger is not only sensitive to INSERT operations, but also to DELETE operations. We can modify the event type and execution statement of the trigger as needed to meet different needs.

It should be noted that if the trigger has been referenced by other objects (such as views, stored procedures), then any modification in its definition may cause these objects to become invalid. Therefore, before modifying a trigger, it is recommended to confirm whether it is referenced by other objects and operate with caution.

Summary

Oracle triggers are a very important part of the database. They can realize functions such as automated management, data consistency maintenance, and data security assurance by automatically monitoring events. This article describes how to modify row-level triggers and statement-level triggers to meet different needs. In practical applications, we should use triggers flexibly according to specific situations and carefully consider their possible impacts before modifying them.

The above is the detailed content of Let's talk about the modification operation of oracle triggers. For more information, please follow other related articles on the PHP Chinese website!