In Oracle, triggers are named database objects that are automatically executed or fired when certain events occur in a table or view. These events can be INSERT, UPDATE, DELETE, or TRUNCATE operations on the table. Triggers can be used to enforce business rules, perform custom actions, or maintain data integrity.
To implement triggers in Oracle, you can use the CREATE TRIGGER statement followed by the trigger name, timing (BEFORE or AFTER the event), event (INSERT, UPDATE, DELETE, TRUNCATE), and the trigger body (PL/SQL block) that specifies the actions to be performed.
For example, a trigger that updates a timestamp column whenever a row is updated in a table can be created using the following syntax:
CREATE OR REPLACE TRIGGER update_timestamp BEFORE UPDATE ON my_table FOR EACH ROW BEGIN :NEW.last_updated := SYSDATE; END update_timestamp;
After creating the trigger, it will be automatically fired whenever an UPDATE operation is performed on the "my_table" table, updating the "last_updated" column with the current timestamp.
Triggers can be a powerful tool in Oracle databases, but they should be used judiciously as they can have performance implications and make the database harder to maintain. It is important to thoroughly test and validate triggers before deploying them in a production environment.
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What is a trigger type in Oracle?
A trigger type in Oracle is a database object that is automatically executed in response to certain events, such as INSERT, UPDATE, or DELETE operations on a table. Triggers can be defined to perform actions such as enforcing business rules, auditing changes, or automatically updating related tables. There are two main types of triggers in Oracle: row-level triggers and statement-level triggers. Row-level triggers are fired once for each row affected by the triggering event, while statement-level triggers are fired once for each SQL statement that triggers the event.
What is a statement-level trigger in Oracle?
A statement-level trigger in Oracle is a type of trigger that fires once for each SQL statement, regardless of the number of rows affected by the statement. This means that the trigger is executed only once per statement, rather than once for each row that is affected by the statement. Statement-level triggers are useful for performing actions that apply to the entire statement operation, such as validating data integrity or logging events.
What is a trigger statement in Oracle?
A trigger statement in Oracle is a statement that is executed automatically in response to certain events or actions performed on a table or view in a database. Triggers are defined at the database level and can be used to enforce business rules, maintain data integrity, and automate processes. When a trigger is defined for a table, the trigger statement is executed whenever the specified triggering event occurs, such as when a record is inserted, updated, or deleted from the table.
What is a trigger owner in Oracle?
In Oracle, a trigger owner refers to the user who created or owns a specific trigger in a database. The trigger owner has the privileges to manage and modify the trigger as needed. The trigger owner can be a specific user or a role granted the necessary permissions to create, alter, or drop triggers in the database.
What is a trigger impact in Oracle?
A trigger impact in Oracle refers to the effects that a trigger has on the database when it is activated. Triggers in Oracle are special types of stored procedures that are automatically executed (or fired) when certain events occur in the database. These events can include actions such as inserting, updating, or deleting data from a table.
When a trigger is fired, it can have various impacts on the database, such as updating data in other tables, enforcing constraints, auditing changes, or performing calculations. The trigger impact refers to the changes that are made to the database as a result of the trigger being fired. Triggers are commonly used in Oracle databases to enforce business rules, maintain data integrity, and automate certain tasks.
