A trigger is a named PL/SQL unit that is stored in the database and fired in response to a specified event that occurs in the database.
The specified event is associated with either a table, a view, a schema, or the database, and it is one of the following:
The trigger is said to be defined on the table, view, schema, or database.
A DML trigger is fired by a DML statement, a DDL trigger is fired by a DDL statement, the DELETE trigger is fired by the DELETE statement, and so on.
A system trigger is defined on a schema or the database. A trigger defined on a schema fires for each event associated with the owner of the schema (the current user). A trigger defined on a database fires for each event associated with all users.
A simple trigger can fire at exactly one of the following timing points:
An INSTEAD OF trigger is a DML trigger that is defined on a view (not a table). The database fires the INSTEAD OF trigger instead of executing the triggering DML statement.
Edit a trigger by selecting Edit Trigger from the Database Explorer node shortcut menu. In the opened document, you can alter the query text. Save the document to apply changes you’ve made to the query text.
Drop a Trigger by selecting Delete from the Database Explorer node shortcut menu.
Enable or disable a trigger by selecting Enable or Disable from the Database Explorer node shortcut menu.
To enable or disable all triggers at once, select Enable All or Disable All from the Database Explorer node shortcut menu.