What does triggers mean in use case and what are the trigger

What does triggers mean in use case, and what are the trigger types? and who\'s usually be a trigger?

Solution

Triggers:

Triggers supplement the standard capabilities of Oracle to provide a highly customized database management system.Excessive use of triggers can result in complicated interlinks, which can be complex in maintaining a large application.So,triggers are used only when necessary.

A trigger leads the Use case to start,so the trigger seems to be as an initiator of a use class.

Types of triggers:

  Row triggers are useful if the code in the trigger action depends on data provided by the triggering statement or rows that are affected.

Statement triggers are useful if the code in the trigger action does not depend on the data provided by the triggering statement or the rows affected.

BEFORE and AFTER Triggers:

BEFORE triggers run the trigger action before the triggering statement is run.

AFTER triggers run the trigger action after the triggering statement is run.

INSTEAD OF Triggers:

INSTEAD OF Triggers are used to modify the aspects that cannot be modified directly through DML statements.

Triggers on System Events and User Events:

Triggers on system events can be defined at the database level or schema level.Triggers on DML statements can be defined on a table or view. A trigger defined at the database level fires for all users, and a trigger defined at the schema or table level fires only when the triggering event involves that schema or table.